Association between body mass index and estimated glomerular filtration rate in patients with chronic kidney disease of unknown aetiology in Sri Lanka

Chronic kidney disease of unknown aetiology (CKDu), which is widespread in the North Central Province (NCP) of Sri Lanka, is not associated with commonly known factors such as diabetes, hypertension, and glomerulonephritis. The pathogenicity of CKDu is not well understood, but people with a low body mass index (BMI) and mineral and nutrient deficiencies are more vulnerable to develop CKDu. To understand this situation, the relationship between BMI and the estimated glomerular filtration rate (eGFR) was investigated in people with CKDu in comparison with unaffected age-matched control groups in disease-endemic areas of the NCP. This community-based cross-sectional study was performed in Medirigiriya in the Polonnaruwa district of Sri Lanka, which has one of the highest densities of patients with CKDu. The data for identifying demographic factors and the relationship between CKDu and BMI were investigated by using a validated survey questionnaire. Findings indicated that the group with the highest number of people affected with CKDu (i.e. eGFR of less than 60 mL/min/1.73 m²) had the lowest BMI compared to those with normal eGFR. The majority affected were male farmers. The severity of the disease was inversely associated with BMI values and had a higher prevalence of smoking and alcohol consumption. In addition, those who consume water from household dug wells had significantly lower eGFR (p < 0.0001). A linear regression analysis revealed a significant positive association between lower eGFR and lower BMI (p < 0.001). We hypothesised that the low BMI in those with CKDu may have increased susceptibility to develop CKDu, in the presence of exposure to multiple nephrotoxins and adverse conditions.

Vitamin D: Effects on human reproduction, pregnancy, and fetal well-being

Pregnancy places exceptional demands on vitamin D and calcium availability; thus, their deficiencies during pregnancy threaten the woman and her fetus. Globally, vitamin D and other micronutrient deficiencies are common during pregnancy, especially in developing countries where pregnant women have less access to nutritional supplements. Vitamin D deficiency has been reported to be as high as 40% among pregnant women. As a pregnancy progresses, the requirements for vitamin D increase and thus, can worsen preexisting hypovitaminosis D. Consequently, hypovitaminosis D is increasingly associated with a higher incidence of fetal miscarriage, preeclampsia, gestational diabetes, bacterial vaginosis, and impaired fetal and childhood growth and development. This review explores the recent advances in the understanding of vitamin D and the pivotal role it plays in human reproduction, with an emphasis on pregnancy and its outcomes. Given the seriousness of the issue, there is a pressing need for clinicians to become aware of the risks associated with not identifying and correcting vitamin D deficiency. Identifying and correcting vitamin D deficiency, including safe exposure to sunlight, is particularly relevant for those who seek assistance with fertility issues or prenatal counseling, and those in the beginning of their pregnancy. The data point to a significant protective effects of vitamin D during pregnancy when the 25(OH)D serum level exceeds 30 ng/mL before pregnancy and during the first trimester and, sufficient levels are maintained throughout the pregnancy.

Mesenteric arterial relaxation to calcitonin gene-related peptide is increased during pregnancy and by sex steroid hormones

The present study investigated whether pregnancy and circulatory ovarian hormones increase the sensitivity of the mesenteric artery to calcitonin gene-related peptide (CGRP)-induced relaxation and possible mechanisms involved in this process. Mesenteric arteries from young adult male rats or female rats (during estrous cycle, after ovariectomy, at Day 20 of gestation, or Postpartum Day 2) were isolated, and the responsiveness of the vessels to CGRP was examined with a small vessel myograph. The CGRP (10(-10) to 10(-7) M) produced a concentration-dependent relaxation of norepinephrine-induced contractions in mesenteric arteries of all groups. Arterial relaxation sensitivity to CGRP was significantly (P < 0.05) greater in female rats compared with male rats. Pregnancy increased the sensitivity to CGRP significantly (P < 0.05) compared to ovariectomized and Postpartum Day 2 rats. In pregnant rats, CGRP-receptor antagonist, CGRP(8-37), inhibited the relaxation responses produced by CGRP. The CGRP-induced relaxation was not affected by N(G)-nitro-l-arginine methyl ester (nitric oxide inhibitor, 10(-4) M) but was significantly (P < 0.05) attenuated by an inhibitor of guanylate cyclase (1H-[1 , 2 , 4 ]oxadizaolo[4 , 3 -a]quinoxalin-1-one, 10(-5) M). Relaxation responses of CGRP on mesenteric arteries were blocked (P < 0.05) by a cAMP-dependent protein kinase A inhibitor, Rp-cAMPs (10(-5) M). The CGRP-induced vasorelaxation was significantly (P < 0.05) attenuated by calcium-dependent (tetraethylammonium, 10(-3) M), but not ATP-sensitive (glybenclamide, 10(-5) M), potassium channel blocker. Therefore, the results of the present study suggest that mesenteric vascular sensitivity to CGRP is higher during pregnancy and that cAMP, cGMP, and calcium-dependent potassium channels appear to be involved. Therefore, we propose that CGRP-mediated vasodilation may be important to maintain vascular adaptations during pregnancy.

Female Sex Steroid Hormones and Pregnancy Regulate Receptors for Calcitonin Gene-Related Peptide in Rat Mesenteric Arteries, but Not in Aorta1

Calcitonin gene-related peptide (CGRP) is a potent vasodilator neuropeptide known to be involved in the regulation of vascular tone. Results of previous studies from our laboratory and others suggest that vascular sensitivity to CGRP is enhanced during pregnancy and that the female sex steroid hormones estradiol-17beta (E2) and progesterone (P4) may be involved in this process. We hypothesized that CGRP receptors in the mesenteric artery are increased during pregnancy and with sex steroid hormone treatments. In the present study, we investigated whether pregnancy and female sex steroid hormones modulate the CGRP-receptors CGRP-A and CGRP-B in the mesenteric artery in the rat. The CGRP-A receptor consists of calcitonin receptor-like receptor (CRLR) and receptor activity-modifying protein 1 (RAMP1); however, the CGRP-B receptor needs to be further characterized. Messenger RNA levels for CRLR and RAMP1 were assessed by reverse transcription-polymerase chain reaction, and CGRP-B receptor proteins levels were determined by Western blot analysis. In addition, [125I]CGRP binding was measured by Scatchard analysis. Both mRNA for CGRP-A (CRLR and RAMP1) and the protein for CGRP-B receptors in mesenteric arteries were increased with pregnancy compared to nonpregnant, diestrous animals. A P4 antagonist, RU-486, downregulated and P4 upregulated these receptors in mesenteric arteries (P < 0.05) in pregnant rats. In adult ovariectomized rats, P4 upregulated CRLR and RAMP1 mRNA levels as well as [125I]CGRP-binding sites. The CGRP-B-receptor protein levels were significantly (P < 0.05) elevated by P4 and by combined E2 and P4 treatment. Together with earlier findings, these data suggest that increases in the expression of CGRP-A (CRLR and RAMP1) and CGRP-B receptors in mesenteric arteries may be important in reducing vascular resistance and in vascular adaptations that occur during pregnancy; in addition, P4 may be involved in this process.

Studies on the effects of the N-terminal domain antibodies of calcitonin receptor-like receptor and receptor activity-modifying protein 1 on calcitonin gene-related peptide-induced vasorelaxation in rat uterine artery

The vascular relaxation sensitivity to calcitonin gene-related peptide (CGRP) is enhanced during pregnancy, compared with nonpregnant human and rat uterine arteries. In the rat uterine artery, two types of CGRP receptors have been shown to coexist, CGRP-A receptor, which is a complex of calcitonin receptor-like receptor (CRLR), and receptor activity-modifying protein (RAMP(1)) and CGRP-B receptor, which is different from CRLR. In the present study, we hypothesized that: 1) CGRP-induced vasorelaxation in rat uterine artery is mediated through CGRP-A receptor and 2) N-terminal (Nt) domain of CRLR (Nt-CRLR) has a major contribution in ligand binding and mediating CGRP- induced relaxation effects in rat uterine artery. Polyclonal antibodies against Nt-domain of CRLR and RAMP(1) (Nt-RAMP(1)) were raised in rabbits and characterized for their specificity and were used to inhibit CGRP-induced vasorelaxation in rat uterine artery. For vascular relaxation studies, uterine arteries from Day 18 pregnant rats were isolated, and responsiveness of the vessels to CGRP was examined with a small vessel myograph. CGRP (10(-10) to 10(-7) M) produced a concentration-dependent relaxation of norepinephrine-induced contractions in Day 18 pregnant rat uterine arteries. These effects were significantly (P < 0.05) inhibited when uterine arteries were incubated with the antibody raised against Nt-CRLR (PD(2) = 6.75 +/- 0.20) and were totally abolished in presence of antibodies for both Nt-CRLR and Nt-RAMP(1) (PD(2) = 6.14 +/- 0.35). In contrast, a monoclonal antibody for CGRP-B receptor had no effect on CGRP-induced rat uterine artery relaxation. These studies suggest that CGRP effects in rat uterine artery are mediated through CGRP-A receptor and that Nt-domain of CRLR may play a predominant role in CGRP binding and thus in causing CGRP-induced uterine artery relaxation.

Mechanisms involved in calcitonin gene-related Peptide-induced relaxation in pregnant rat uterine artery

Human and rodent studies have demonstrated that calcitonin gene-related peptide (CGRP), a potent vasodilator, relaxes uterine tissue during pregnancy but not during labor. The vascular sensitivity to CGRP is enhanced during pregnancy, compared to nonpregnant human uterine arteries. In the present study, we hypothesized that uterine artery relaxation effects of CGRP are enhanced in pregnant rats compared to nonpregnant diestrus rats (NP-DE) and that several secondary messenger systems are involved in this process. We also hypothesized that the expression of CGRP-A receptor components, calcitonin receptor-like receptor (CRLR), receptor activity-modifying protein (RAMP1), and CGRP-B receptors are greater in pregnant rats. For vascular relaxation studies, uterine arteries from either NP-DE or Day 18 pregnant rats were isolated, and responsiveness of the vessels to CGRP was examined with a small vessel myograph. CGRP-A and CGRP-B receptor expressions were assessed by RT-PCR and Western immunoblotting, respectively. CGRP (10(-10)--10(-7) M) produced a concentration-dependent relaxation of norepinephrine-induced contractions in both NP-DE and Day 18 pregnant rat uterine arteries. Pregnancy increased the vasodilator sensitivity to CGRP significantly (P < 0.05) compared to NP-DE rats. CGRP receptor antagonist, CGRP8-37, inhibited CGRP-induced relaxation of pregnant uterine arteries. The CGRP-induced relaxation was not affected by NG-nitro-l-arginine methyl ester (L-NAME) (nitric oxide inhibitor, 10(-4) M) but was significantly (P < 0.05) attenuated by inhibitors of guanylate cyclase (ODQ, 10(-5) M) and adenylate cyclase (SQ 22536, 10(-5) M). CGRP-induced vasorelaxation was significantly (P < 0.05) attenuated by potassium channel blockers KATP (glybenclamide, 10(-5) M) and K(CA) (tetraethylammonium, 10(-3) M). The expression of CRLR and RAMP1 was significantly (P < 0.05) elevated during pregnancy compared to nonpregnant diestrus state (NP-DE). However, CGRP-B receptor proteins in uterine arteries were not altered with pregnancy compared to those of NP-DE. These studies suggest that CGRP-induced increases in uterine artery relaxation may play a role in regulating blood flow to the uterus during pregnancy and, therefore, in fetal growth and survival.

NK1, NK2, NK3 and CGRP1 receptors identified in rat oral soft tissues, and in bone and dental hard tissue cells

The distribution of the tachykinin receptors neurokinin-1 (NK1), neurokinin-2 (NK2) and neurokinin-3 (NK3), and the calcitonin gene-related peptide-1 (CGRP1) receptor were examined in rat teeth and tooth-supporting tissues by immunohistochemical methods and light and confocal microscopy. Western blot analysis was performed to identify the NK1- and the CGRP1-receptor proteins in the dental pulp. The results showed that odontoblasts and ameloblasts, cementoblasts and cementocytes, osteoblasts and osteocytes are all supported with the tachykinin receptors NK1 and NK2, but a distinct, graded cellular labeling pattern was demonstrated. The ameloblasts were also positive for CGRP1 receptor. Blood vessels in oral tissues expressed the tachykinin receptors NK1, NK2 and NK3, and the CGRP1 receptor. Both gingival and Malassez epithelium were abundantly supplied by NK2 receptor. Pulpal and periodontal fibroblasts demonstrated NK1 and NK2 receptors. Western blot analysis identified both the NK1- and the CGRP1-receptor proteins in the dental pulp. These results clearly indicate that the neuropeptides substance P, neurokinin A, neurokinin B and CGRP, released from sensory axons upon stimulation, directly modulate the function of the different types of bone and dental hard tissue cells, and regulate functions of blood vessels, fibroblasts and epithelial cells in oral tissues.

Sex steroid hormones enhance hypotensive effects of calcitonin gene-related Peptide in aged female rats

The aim of the present study is to investigate whether vascular protective effects of steroid hormones in aged female rats are mediated through calcitonin gene-related peptide (CGRP), a known potent vasodilator. This rat model reflects the postmenopausal state in humans. We examined whether blood pressure lowering effects of CGRP are enhanced in aged female rats when steroid hormone treatments are administered. We observed that 1) continuous infusion of CGRP lowered blood pressures in rats treated with estradiol-17beta and progesterone (P < 0.05), 2) acute hypotensive effects of CGRP were significantly (P < 0.05) greater in the presence of steroid hormones than in vehicle-treated groups, 3) blood pressure decreases in response to CGRP are lower in aged female rats than they are in young adult ovariectomized rats, and 4) age-related differences in the hypotensive effects of CGRP were nullified when animals were treated with steroid hormones. These data suggest that female sex steroid hormones may modulate arterial blood pressure by regulating the CGRP effector system in female rats regardless of age.

Effects of pregnancy and female sex steroid hormones on calcitonin gene-related peptide content of mesenteric artery in rats

Calcitonin gene-related peptide (CGRP) levels in plasma and the dorsal root ganglia (DRG) are increased during pregnancy and in ovariectomized rats injected with ovarian hormones. Vasodilatory responses to CGRP are also increased in these animals. In the present study, we hypothesized that pregnancy and ovarian hormones elevate the contents of CGRP in perivascular nerves. We assessed CGRP-dependent mesenteric vascular relaxation induced by electrical field stimulation (EFS) and arterial content of CGRP. Because the mesenteric artery represents resistance vessels, segments of mesenteric arteries collected from female rats at different stages of the estrous cycle, pregnancy, or postpartum and from male rats were used in this study. The EFS-induced relaxation in the presence and absence of CGRP(8-37), an antagonist of CGRP, was used to measure CGRP-dependent relaxation, and radioimmunoassay (RIA) of tissue homogenates was used to assess changes in CGRP content in mesenteric branch arteries. The results show that CGRP-dependent, EFS-induced relaxation response was lower in female rats at diestrus and proestrus than in male rats, and no statistically significant differences were observed between Gestational Day 20 and Postpartum Day 2. The RIA revealed significantly lower mesenteric artery CGRP levels in female rats at proestrus, gestation, and postpartum than in female rats at diestrus or in male rats. We conclude that no correlation exists between CGRP-dependent, EFS-induced relaxation and CGRP content in the mesenteric arteries of these animal groups. Because both CGRP levels in DRG and serum are reported to be elevated, the reduced CGRP content in the vasculature during pregnancy and proestrus implicate enhanced basal release of CGRP at the nerve terminal in these animals.

Infusion of pregnant rats with calcitonin gene-related peptide (CGRP)(8-37), a CGRP receptor antagonist, increases blood pressure and fetal mortality and decreases fetal growth

Calcitonin gene-related peptide (CGRP) is the most potent endogenous vasodilatory peptide, and is involved in the regulation of blood flow to vital organs. We have previously shown that CGRP may be involved in vascular adaptations that occur during pregnancy, and that steroid hormones may be involved in these mechanisms. We hypothesized that endogenous CGRP is required for maintaining blood pressure and fetoplacental growth in pregnant rats, and that progesterone will enhance CGRP effects. The vasodilatory effects of CGRP are known to be inhibited by a competitive CGRP receptor antagonist, the C-terminal fragment CGRP(8-37). In the present study, we investigated whether continuous s.c. infusion of CGRP(8-37) to pregnant rats will reduce fetoplacental growth and increase systolic blood pressure. We also assessed whether progesterone will alter the effects of CGRP(8-37) on blood pressure during postpartum. Groups of five pregnant rats were s.c. infused with varying doses of CGRP(8-37) from Day 17 of pregnancy. Daily systolic blood pressures, pup weight, mortality at term delivery, and fetoplacental weights on Day 20 of gestation were measured. CGRP(8-37) at a dose of 0.083 mg day(-1) kg(-1) body weight (BW) showed no effects; however, doses of 0.33 and 1.33 mg day(-1) kg(-1) BW increased (P < 0.05) blood pressure during pregnancy, and these elevated blood pressures persisted during postpartum with the highest dose used. Progesterone (2 mg per injection, twice a day; s.c.) treatment significantly elevated blood pressure in rats infused with CGRP(8-37) during postpartum, suggesting that progesterone regulates CGRP-induced vascular effects. CGRP(8-37) infusion caused significant reductions in pup weight with an increase in mortality rate, and these effects were dose-dependent. Placental and fetal weights were also decreased prior to term on Day 20 of gestation, 72 h after CGRP(8-37) infusion, indicating effects on uteroplacental tissues. Therefore, we suggest that endogenous CGRP plays an important role in maintaining normal fetoplacental development, fetal survival, and vascular adaptations during pregnancy.

Pregnancy and steroid hormones enhance the systemic and regional hemodynamic effects of calcitonin gene-related peptide in rats

Calcitonin gene-related peptide (CGRP) is a potent vasodilator neuropeptide known to be involved in the regulation of vascular resistance. Several lines of evidence suggest that CGRP plays a role in the vascular adaptations that occur during normal pregnancy; however, the effects of exogenous CGRP on systemic and regional hemodynamics during pregnancy remain unknown. Therefore, the purpose of this study was to determine the hemodynamic effects of systemically administered CGRP in adult pregnant (Day 19) and ovariectomized (ovx) rats using the radioactive microsphere technique. In addition, we also used ovariectomized rats treated for 3 days with estradiol (E2), progesterone (P4), E2 + P4 in sesame oil, or oil only to assess if these hormones regulate the CGRP-induced hemodynamic changes. On the day of study, catheters were inserted into the left cardiac ventricle (through the right carotid artery), right jugular vein, and caudal tail artery. Hemodynamic studies using radioactive microspheres were then performed in conscious rats 3 h after recovery from anesthesia. Blood pressure and heart rate were continuously monitored, and left ventricular pressure was determined immediately prior to each microsphere injection. Microspheres labeled with either (141)Ce or (85)Sr were injected prior to and 2 min following the i.v. bolus injection of CGRP (270 pmol/kg body weight [BW]). Mean arterial pressure (MAP) and total vascular resistance in pregnant rats was lower than in ovx rats, and this was further decreased with an i.v. bolus injection of 270 pmol CGRP/kg BW. Cardiac output was elevated with further increases upon CGRP administration in pregnant but not in ovx rats. The CGRP-induced changes in MAP, total vascular resistance, and cardiac output in E2 + P4 -treated rats were similar to that observed in Day 19 pregnant rats, indicating that CGRP effects on these parameters during pregnancy may be modulated by steroid hormones. Both pregnancy and E2 + P4 treatment in ovx rats caused significant decreases in CGRP-induced resistance in mesenteric, coronary, and renal vasculature. Thus, the vasodilatory sensitivity to CGRP during pregnancy may be mediated through decreased total vascular resistance, particularly to coronary, mesenteric, and renal vascular beds. Thus, CGRP-induced vasodilatory effects may play a role in mediating vascular adaptations that occur during pregnancy and that steroid hormones may modulate these CGRP effects.

Distribution of amylin-immunoreactive neurons in the monkey hypothalamus and their relationships with the histaminergic system

Amylin (AMY) is a 37 amino acid peptide of pancreatic origin that has been localized in peripheral and central nervous structures. Both peripheral and central injection of the peptide causes various effects, including anorectic behavior in rats. Prompted by previous reports showing that the anorectic effect of AMY is mediated by histamine release, we immunohistochemically investigated possible relationships between these two systems at the light microscopical level. Monkey (Macaca fuscata japonica) hypothalamus specimens were submitted to immunohistochemical double staining procedures using AMY and histidine decarboxylase (HDC) antisera. AMY-immunoreactive neurons were found widely distributed in several nuclei of the monkey hypothalamus including the supraoptic, paraventricular, perifornical, periventricular, ventromedial, arcuate, and tuberomammillary nuclei. We detected AMY-immunoreactive nerve fibers throughout the hypothalamus, the median eminence and hypothalamus-neurohypophysial tract. Although AMY- and HDC-immunoreactive neuronal cell bodies occupied distinct hypothalamic zones, many HDC-immunoreactive cell bodies and dendrites, particularly those in the periventricular, arcuate, and rostral tuberomammillary regions, were surrounded by numerous AMY-immunoreactive nerve fiber varicosities. These findings demonstrate for the first time the presence of a discrete number of AMY-immunoreactive neurons in the monkey hypothalamus and add morphological support to the experimental data demonstrating that AMY probably exerts its influence on food intake via the histaminergic system.

Calcitonin gene- and parathyroid hormone-related peptides in preeclampsia: effects of magnesium sulfate

OBJECTIVE

To determine whether circulating levels of calcitonin gene-related peptide (CGRP) and parathyroid hormone-related peptide (PTHrP) are altered in preeclampsia, and to assess the effects of magnesium sulfate therapy on circulating levels of these two peptides.

METHODS

The study population included 25 women with preeclampsia and 25 normotensive controls of similar gestational age. The effects of magnesium sulfate therapy were evaluated in 17 of the 25 preeclamptic women. Circulating levels of immunoreactive CGRP and PTHrP, including calcium, magnesium, and phosphate in the maternal and umbilical cord serum were measured.

RESULTS

The frequency of preeclampsia subjects with nondetectable PTHrP (under 3 pg/mL) was significantly higher (92% versus 48%, P <.001), whereas maternal serum CGRP levels were significantly lower (50 +/- 19 versus 90 +/- 23 pg/mL, P <.001). Similarly, the frequency of newborns with nondetectable PTHrP levels in umbilical serum was significantly higher (68% versus 36%, P <.05), whereas the levels of CGRP were significantly lower (67 +/- 17 versus 79 +/- 16 pg/mL, P <.05). Magnesium sulfate treatment resulted in a significant increase in maternal circulating CGRP levels (64 +/- 17 versus 47 +/- 18 pg/mL, P <.05) with no changes in PTHrP.

CONCLUSION

Maternal circulating PTHrP and CGRP concentrations were significantly lower in women with preeclampsia, which may contribute to the development and maintenance of hypertension during pregnancy. Furthermore, magnesium sulfate therapy increased the levels of CGRP in the maternal circulation.

Calcitonin gene-related peptide receptor expression in the neurons and glia of developing rat cerebellum: an autoradiographic and immunohistochemical analysis

Quantitative autoradiography (using [125I]human alpha-calcitonin gene-related peptide as a ligand) and immunofluorescence (using monoclonal antibodies directed against a purified receptor) followed by confocal analysis were applied to analyse the distribution and cellular localization of the calcitonin gene-related peptide receptor in the rat cerebellum during development. From late embryonic days to the end of the second postnatal week, during the time window of calcitonin gene-related peptide expression in climbing fibers, high levels of calcitonin gene-related peptide binding sites were found in the white matter, where immunolabeling was present in oligodendrocytes. Lower levels were found in the cerebellar cortex, where receptor immunolabeling was found in Bergmann glia in a presumptive cell surface location and, during the second postnatal week, also in the cytoplasm of Purkinje cells. From the end of the second postnatal week to adulthood, when calcitonin gene-related peptide is no longer present in climbing fibers, the number of calcitonin gene-related peptide binding sites increased in the molecular layer, where not only Bergmann glia but also Purkinje cell distal dendritic branchlets were immunolabeled in a presumptive cell surface location. Concomitantly, the number of calcitonin gene-related peptide binding sites sharply decreased in the white matter. The developmental expression of the calcitonin gene-related peptide receptor and the previously described proliferating/differentiating effects of the peptide on glial cells suggest that calcitonin gene-related peptide and its receptor may promote a coordinated development of cerebellar glial cells, an effect driven mainly by the calcitonin gene-related peptide released by climbing fibers. As a result of glia-neuron interactions, an indirect effect on the differentiation of the cerebellar neuronal circuitry is also likely to occur.

Arthritic calcitonin/alpha calcitonin gene-related peptide knockout mice have reduced nociceptive hypersensitivity

Peripheral inflammation induced with a knee joint injection of a mixture of kaolin/carrageenan (k/c) produces primary and secondary hyperalgesia. Inflammatory pain is thought to involve a variety of transmitters released from nerve terminals, including amino acids, substance P (SP) and calcitonin gene-related peptide (CGRP). In the present study, mice deficient in the calcitonin/alpha CGRP gene (CGRP(-/-)) displayed normal responses to noxious stimuli. However, the CGRP knockout mice failed to demonstrate development of secondary hyperalgesia after induction of knee joint inflammation in two tests that assess central sensitization, through testing at sites remote from the primary insult. Nociceptive behavioral responses were assessed using the hot-plate test and paw withdrawal latency (PWL) to radiant heat applied to the hindpaw. The CGRP(-/-) mice showed no signs of secondary hyperalgesia after development of knee joint inflammation, while the expected significant decrease in the PWL was observed in the CGRP(+/+) mice as control. The CGRP(-/-) mice also had a prolonged rather than a shortened response latency in the hot-plate test 4 h after knee joint injection of k/c. Immunohistological study showed that CGRP-like immunoreactivity (CGRP-LI) was absent in the spinal cord and dorsal root ganglia taken from the CGRP(-/-) mice. These results indicate that endogenous CGRP plays an important role in the plastic neurogenic changes occurring in response to peripheral inflammatory events including the development of nociceptive behaviors.

The mechanism of bone resorption by cyclosporin: involvement of the NO-cGMP pathway

Treatment with cyclosporin A (CsA) following solid organ transplantations such as heart or liver generally results in bone loss. However, in vitro studies show that CsA inhibits bone resorption. Our previous in vivo animal studies demonstrated that the effects of nitric oxide (NO) on bone are biphasic; at high doses, NO increases bone resorption. In this study, we have examined in an in vitro setting to determine whether the bone loss caused by CsA administration is dependent on the NO-cyclic guanosine monophosphate (cGMP) pathway. Freshly isolated osteoclast-rich neonatal rat long bone marrow cells were added to 100 microM thick dentin sections that had been seeded with neonatal-rat calvarial osteoblasts. These co-cultures were maintained for 48 hrs in a basal medium with CsA (1, 5, and 10 microg/ml), both alone and with either L-Arginine (NO substrate; 10-3M), L-NAME (NO synthase enzyme inhibitor; 10-4M), or the combination of the two. The cultures were then fixed in cold 95% ethanol and stained with tartrate resistant acid phosphatase (TRAP) to identify osteoclasts and sites of osteoclastic resorption. Preparations were analyzed using an automated histomorphometry software package. Scanning electron microscopy affirmed that the areas identified by light microscopy as resorption sites contained osteoclastic lacunae. CsA inhibited bone resorption dose-dependently. CsA at 10 microg/ml produced a 90% inhibition of bone resorption (control = 5.5 -/+2.0%; CsA = 0.64 -/+ 0.09=). L-Arginine reversed this inhibition by 90% (Arg + CsA = 4.23 -/+ 1.57%; CsA = 0.64 -/+ 0.09%). The application of NOS inhibitor L-NAME inhibited bone resorption by 87% (Arg + CsA + L-NAME = 0.55 -/+ 0.14%; Arg + CsA = 4.23 -/+ 1.5%). We conclude that NO-cGMP pathway is involved in the CsA induced bone loss.

Immunohistochemical localization of amylin in rat brainstem

Immunohistochemical studies were conducted on rat brainstem using a specific polyclonal antiserum against the COOH-terminal (25-37) of human amylin. Amylin-immunoreactive cell bodies were observed in the vestibular, cochlear, trapezoid, and inner cerebellar nuclei and in the mesencephalic nucleus of trigeminal nerve. Positive cell bodies were also found in lateral, gigantocellular and magnocellular reticular nuclei. Numerous amylin-immunoreactive nerve fibers were shown in the trigeminal spinal tract, in the solitary area and in the area postrema. Amylin-immunoreactive cell bodies were often surrounded by a network of tyrosine hydroxylase-immunoreactive nerve fibers. These results provide morphologic evidence that amylin may play a role in some discrete sensory functions.

Nitroglycerin therapy is as efficacious as standard estrogen replacement therapy (Premarin) in prevention of oophorectomy-induced bone loss: a human pilot clinical study

Nitric oxide (NO) is known to affect bone metabolism. Previous animal studies have shown that NO donor therapy can prevent ovariectomy (OVX)-induced as well as corticosteroid-induced bone loss. Therefore, we have carried out a 1-year human, randomized, controlled pilot clinical study to assess the efficacy of nitroglycerin (NG) in the prevention of estrogen-deficiency-induced bone loss in women. We observed that NG ointment, when applied to the skin once a day (within 4 weeks of undergoing oophorectomy), mimicked estrogen replacement therapy in prevention of bone loss. The primary outcome of bone mineral density (BMD) was not different in the two groups at the end of 1 year. Urinary N-telopeptide levels were significantly decreased after administration of either estrogen or NG. Although estrogen decreased serum osteocalcin and bone-specific alkaline phosphatase levels, NG therapy significantly increased these two markers of bone formation. Further, it was revealed that for up to 1 year, these doses of NG did not result in tachyphylaxis. This study showed for the first time that NG is as effective as estrogen in preventing bone loss in these surgically induced menopausal women. Additionally, the dose of NG used in this study was three to four times less than that generally used to affect cardiovascular homeostasis. Although in this randomized clinical study only a small number of patients was examined, data are encouraging. If these data hold true in large randomized, controlled clinical trials, then NG could emerge as an efficacious, cost-effective, affordable, safe, and convenient form of therapy (especially as an alternative therapy to hormone-replacement therapy [HRT]) for prevention of postmenopausal bone loss.

A novel pharmacological approach of musculoskeletal losses associated with simulated microgravity

Exposure to microgravity (weightlessness) is known to cause rapid bone and muscle losses. We have used the hind limb-suspended (HLS) rat model to simulate microgravity-induced musculoskeletal losses in order to assess resulting hormonal changes and to develop a novel pharmacological countermeasure. Previously, we demonstrated significant decreases in circulatory hormonal levels [serum thyroxin, 1,25(OH)2 vitamin D (p<0.05), and serum testosterone (p<0.001)] in HLS rats. Both thyroxin and 1,25(OH)2 vitamin D levels returned to normal soon after removal from HLS, while testosterone levels matched normal levels only after a further 3-4 weeks. However, even by day 42, bone mineral density (BMD) remained significantly lower, although serum hormones were back to normal. Because serum testosterone levels become undetectable in HLS rats, we hypothesized that the replacement of testosterone during HLS could prevent musculoskeletal losses. Based on these data, an intervention study was carried out to assess the efficacy of testosterone and synthetic anabolic steroid, nandrolone decanoate (ND), in prevention of weightlessness-induced musculoskeletal losses. HLS rats (control) had a significant reduction of muscle volume (42.9 -/+ 3.0, versus 56 -/+ 1.8 in ground control rats; p<0.01). Both testosterone and ND treatments prevented this muscle loss (51.5 -/+ 2 cm(3) and 51.6 -/+ 1.2, respectively; a 63% improvement, p<0.05). Similarly, BMD of the placebo-treated HLS rats was significantly lower than that of ground control rats (0.416 -/+ 0.011 versus 0.354 -/+0.014, p<0.05), and testosterone and ND prevented this bone loss (0.404 -/+ 0.013 versus. 0.409 -/+ 0.011, respectively). These data suggest that both testosterone and ND therapy can minimize the musculoskeletal losses associated with exposure to simulated weightlessness. Experiments using the combination of bisphosphonate and testosterone demonstrated complete protection of both muscle and bone in these HLS rats. Therefore, considering that: 1) testosterone is anabolic to osteoblasts and muscle cells and also decreases the rate of bone turnover, 2) serum testosterone levels are markedly suppressed in simulated weightlessness, and 3) testosterone replacement therapy prevented musculoskeletal losses in HLS rats, we propose that the musculoskeletal losses observed in this animal model (i.e., simulated microgravity) are related to their testosterone deficiency. Since serum sex hormones levels are markedly reduced in this model of simulated microgravity, androgen replacement with a bisphosphonate seems to be a rational counter.

Pregnancy and sex steroid hormones enhance circulating calcitonin gene-related peptide concentrations in rats

Calcitonin-gene-related peptide (CGRP) is a 37 amino acid neuropeptide synthesized primarily in dorsal root ganglia (DRG) and distributed widely in the perivascular nerves, suggesting that this peptide may play a role in the regulation of peripheral vascular tone. Since female sex steroid hormones have been implicated in the regulation of peripheral vascular tone during pregnancy, we postulated that they may alter the concentration of CGRP in the circulation and thus modulate the increased blood flow observed during pregnancy. In the present study, we measured changes in plasma concentrations of CGRP in non-pregnant, pregnant, and post-partum rats. Groups of ovariectomized rats were treated s.c. for 3 days either with 17beta-oestradiol (2.5 microg per injection twice daily), progesterone (2 mg per injection twice daily), or vehicle. Another group of adult, non-pregnant rats at dioestrus stage of the oestrous cycle was also used in this study. Plasma concentrations of CGRP were higher (P < 0.05) in rats on day 19 of pregnancy (22.0 +/- 3.0 pmol/l) compared to that during delivery (5. 0 +/- 2.0), post-partum day 2 (2.0 +/- 0.7) or in non-pregnant (4.9 +/- 1.6) state. Furthermore, in adult ovariectomized (6.0 +/- 0.6) rats, plasma CGRP concentrations were increased significantly (P < 0. 05) by oestradiol (10.0 +/- 1.0), progesterone (9.5 +/- 1.0) and oestradiol + progesterone (14.0 +/- 1.0). Thus, circulating concentrations of CGRP are elevated during pregnancy and by oestrogen and progesterone, suggesting that the elevated concentrations of CGRP may play an important role in vascular adaptations that occur during pregnancy.

Restoration of ovariectomy-induced osteopenia by nitroglycerin

Nitric oxide (NO) is known to inhibit osteoclastic bone resorption. Previously, we demonstrated that the NO donor nitroglycerin (NG) prevented ovariectomy (OVX)-induced bone loss. The current study shows that NG restores ovariectomy-induced osteopenia. Twenty-four female Sprague-Dawley rats, 36 weeks of age, underwent OVX, and a further six rats were sham-operated. Bone mineral density (BMD) was measured by dual-energy X-ray absorptiometric (DXA) scanning prior to OVX, at 6 weeks postsurgery, and at 6 weeks posttreatment. OVX rats were then assigned to four groups and treated with either (1) vehicle, (2) 17-beta-estradiol, (3) NG (0.2 mg/kg/day), or (4) a combination of estrogen and NG (n = 6/group). During the first 6-week post-OVX period, there was a significant decrease in the BMD in all ovariectomized (OVXed) rats (-11.0%, P < 0.001). There were no significant changes in BMD during the entire 12-week period in sham-operated rats. During the second 6-week period (after developing bone loss), there was no further significant loss of BMD in OVXed controls. BMD loss and loss of femur weight produced by OVXed were restored by treatment with estrogen, NG, or the two agents together during the second 6-week period (P < 0.01). The effects of estrogen and NG together, however, were not additive. The BMD of rats treated with NG alone, at 12 weeks, was similar to that of animals treated with estrogen alone or with estrogen and NG, and was comparable to that of sham-operated rats. The increased urinary excretion of deoxypyridinolines caused by OVX was negated by estrogen, NG, and estrogen together with NG (P < 0.01). In contrast to estrogen, NG did not decrease the post-OVX-induced increase of serum osteocalcin levels, suggesting that NG may also have a positive effect on bone formation. In summary, the results suggest that the NO donor, NG, reverses the OVX-induced bone loss in rats, and these effects are likely due to decreased bone resorption and, perhaps, increased bone formation.

Increased blood pressure in alpha-calcitonin gene-related peptide/calcitonin gene knockout mice

Nerves that contain calcitonin gene-related peptide (CGRP) are components of the sensory nervous system. Although these afferent nerves have traditionally been thought to sense stimuli in the periphery and transmit the information centrally, they also have an efferent vasodilator function. Acute administration of a CGRP receptor antagonist increases the blood pressure (BP) in several models of hypertension, which indicates that this potent vasodilator plays a counterregulatory role to attenuate the BP increase in these settings. To determine the role of this peptide in the long-term regulation of cardiovascular function, including hypertension, we obtained mice that have a deletion of the alpha-calcitonin gene-related peptide (alpha-CGRP) gene. Although the beta-calcitonin gene-related peptide (beta-CGRP) gene is intact in these mice, alpha-CGRP is by far the predominant species of CGRP produced in dorsal root ganglia (DRG) sensory neurons. Initially, we examined the effect of deletion of the alpha-CGRP on baseline BP and beta-CGRP and substance P mRNA expression. Systolic BP was significantly higher in the knockout mice (n=7) compared with wild-type in both male (160+/-6.1 vs 125+/-4.8 mm Hg) and female (163+/-4.8 vs 135+/-33 mm Hg) mice. Next, groups (n=7) of knockout and wild-type mice had catheters surgically placed in the right carotid artery for mean arterial pressure recording. With the animals fully awake and unrestrained, the knockout mice displayed an elevated mean arterial pressure compared with wild-type in both male (139+/-4.9 vs 118+/-4.9 mm Hg) and female (121+/-3.4 vs 107+/-3.1 mm Hg) mice. Northern blot analysis of DRG RNA samples confirmed the absence of alpha-CGRP mRNA in the knockout mice. Substance P mRNA content in DRG was unchanged between the 2 groups; however, beta-CGRP mRNA levels were reduced 2-fold in the knockout mice. These results indicate for the first time that alpha-CGRP may be involved in the long-term regulation of resting BP and suggest that these mice are particularly sensitive to challenges to BP homeostasis because of the loss of a compensatory vasodilator mechanism.

Prevention and treatment of osteoporosis: efficacy of combination of hormone replacement therapy with other antiresorptive agents

Osteoporosis is a debilitating disease characterized by decreased bone mineral density (BMD) leading to fractures. It primarily affects postmenopausal women and elderly men. Prevention of osteoporosis is very important because present therapies do not have the potential to mend damage to the bone microarchitecture caused by osteoporosis. The first line of prevention and treatment of osteoporosis is hormone replacement therapy (HRT). All of the approved drugs for the prevention and treatment of osteoporosis act as inhibitors of bone resorption; these drugs include HRT, selective estrogen receptor modulators, calcitonin, and bisphosphonates. The latter two drugs have also been shown to prevent fractures. This article discusses data from nine controlled prospective clinical studies. Study 1 was designed to assess the efficacy of combined HRT and bisphosphonate in preventing osteoporosis during the early stages of menopause. This combined therapy increased the lumbar spine BMD by 10.9% and femoral BMD by 7.3% over 4 yr, compared with 6.8 and 4.0% with HRT alone, and 6.8 and 1.2% with bisphosphonate alone. Study 2 was conducted on postmenopausal women with established osteoporosis. These results showed a 10.4 and 7.0% increase in BMD in vertebrae and femora, respectively, compared with 7.3 and 4.8% increases in the HRT group, and 6.8 and 0.9% in the bisphosphonate group. Data from study 3 demonstrated similar findings in that the combination of alendronate and HRT also enhanced BMD values. Studies 4 and 5 assessed the efficacy of the combined therapy of HRT and calcitonin in the prevention of early postmenopausal bone loss. Both studies demonstrated a significant increase in BMD over and above that observed with either HRT or calcitonin alone. Studies 6, 7, and 8 demonstrated that the addition of testosterone to estrogen therapy further increased BMD when compared to estrogen therapy alone, and also prevented the expected decreases in markers of bone formation in early postmenopausal women. Study 9 demonstrated a synergistic effect on BMD in postmenopausal women, when HRT was coadministered with monofluorophosphate. Other combination therapies may also enhance BMD (e.g., the combination of alendronate and parathyroid hormone [PTH]). However, some agents either lose their efficacy or have no added effects on BMD when they are coadministered (e.g., tiludronate and PTH, calcitonin and PTH, calcitonin and anabolic steroids). These studies illustrate that in a subgroup of patients (i.e., patients with high bone turnover and/or severe osteoporosis), specific combination treatments such as HRT with bis-phosphonates, calcitonin, or androgens (and perhaps also with PTH, fluoride, nitric oxide donors) provide additional beneficial effects over a single-drug therapy. Whether these combination therapies are more effective than individual drugs in reducing fractures still needs to be determined.

Involvement of calcitonin gene-related peptide in the modulation of human myometrial contractility during pregnancy

Calcitonin gene-related peptide (CGRP) is a potent vasodilator and relaxes smooth muscle of a variety of tissues, but the effects of CGRP on human myometrial contractions and the changes in CGRP receptors (CGRP-Rs) in human myometrium have not been described. We report that CGRP induced dose-dependent relaxation in spontaneously contracting myometrium from pregnant women. This relaxation effect is diminished in myometrium obtained from patients during labor and in the nonpregnant state. CGRP-induced relaxations are inhibited by a CGRP-R antagonist (CGRP(8-37)), a soluble guanylate cyclase inhibitor (LY(83583)), and a nitric oxide synthase inhibitor (L-NAME). Both Western blotting and mRNA analysis showed that CGRP-Rs are present in human myometrium, and that the expression of these receptors is increased during pregnancy and decreased during term labor. Immunofluorescent staining revealed that CGRP-Rs are abundant in the myometrial cells of pregnant women who are not in labor, and are minimal in uterine specimens from women in labor and in the nonpregnant state. We conclude that increased CGRP-Rs in myometrium, and resulting enhanced myometrial sensitivity to CGRP, may play a role in maintaining human myometrium in a quiescent state during pregnancy, and that a decline in the CGRP-Rs at term could contribute to the initiation of labor.

Receptor for calcitonin gene-related peptide: localization in the dorsal and ventral spinal cord

Although the distribution of calcitonin gene-related peptide has been extensively studied in the spinal cord, little is known about the precise subcellular localization of receptors for calcitonin gene-related peptide. The present study was undertaken to localize calcitonin gene-related peptide receptors in both the dorsal and ventral horns of the rat spinal cord. Immunocytochemical localization with specific monoclonal antibodies was performed at the light and electron microscopic levels. Calcitonin gene-related peptide receptor was expressed in neuronal but not glial elements. Discrete postsynaptic localization of receptor for the calcitonin gene-related peptide was evident in the cells and dendrites of the superficial dorsal horn. Some of the terminal endings apposing the stained synapses formed the central terminals of glomerular complexes. The endings were scallop shaped (Type I), typical of primary afferent terminations. Other dorsal horn structures with postsynaptic labeling were contacted by dome-shaped or elongated axonal endings. Presynaptic localization on some dorsal horn terminations may serve an autoreceptor function. Motoneurons, on the other hand, were contacted by axonal terminals with presynaptic calcitonin gene-related peptide receptors. These data suggest that (i) dorsal horn neurons are capable of direct primary afferent, calcitonin gene-related peptide receptor-mediated interactions and (ii) neuronal terminals contacting motor horn cells can be influenced through presynaptic paracrine-like calcitonin gene-related peptide receptor-mediated interactions. Thus, calcitonin gene-related peptide can have multiple modulatory effects on spinal cord neurons through site-specific receptors.

Simulated weightlessness-induced attenuation of testosterone production may be responsible for bone loss

This study examined the effects of simulated weightlessness on serum hormone levels and their relationship to bone mineral density (BMD). The tail-suspended (i.e., hindlimb suspended, HLS) rat model was used to simulate weightless conditions through hindlimb unloading to assess changes in hormonal profile and the associated bone loss. In the first study, 24 adult male rats were assigned to two groups with 12 rats being HLS for 12 d, and the remaining 12 rats serving as ground controls. On d 0, 6, and 12, blood samples were taken to estimate circulating hormone levels. HLS rats had significant reductions in testosterone, 1,25 (OH)2 vitamin D, and thyroxine levels by d 6 (p<0.01); their testosterone levels were almost undetectable by d 12 (p<0.001). Serum cortisol levels in these rats were elevated on d 6 (p<0.02), but returned to normal levels by d 12. No changes were observed with serum ionized calcium and other hormones examined, as well as the body weights, and weights of thymus, heart, and brain. In the second study, eight rats were ground controls, while an additional eight rats were HLS for 12 d before being removed from tail-suspension and maintained for a further 30 d. Blood samples were collected every 6th d for 42 d. This study showed that both serum thyroxine and 1,25(OH)2 vitamin D levels returned to normal levels soon after hind limb unweighting, while serum testosterone levels matched normal levels only after a further 3-4 wk. These studies showed a significant decrease of femur weights, but not weights of humeri in HLS rats suggesting that this is a specific effect on unloaded bones. On d 12 in both studies, a significant reduction in the lumbar spine (p<0.05) and the femoral neck (p<0.01) BMD appeared in HLS rats. This was confirmed in the second study, where HLS led to a significant decrease in BMD even extending to d 42. Previous studies have shown that space flight and tail-suspension lead to marked reductions in bone formation with little effect on bone resorption. Recently, we reported that androgen replacement can indeed prevent bone losses in this animal model. Therefore, it seems logical to propose that the significant decreases of serum testosterone observed in these tail-suspended animals are, at least in part, responsible for the losses of BMD seen in their affected weight-bearing bones (i.e., lumbar spine and the femur). Considering that 1. testosterone is anabolic to osteoblasts and also decreases the rate of bone turnover 2. serum testosterone levels are markedly suppressed in simulated weightlessness, and 3. testosterone replacement therapy prevented the bone loss in HLS rats, we propose that the testosterone deficiency in this animal model is related to their bone loss.

Reversal of weightlessness-induced musculoskeletal losses with androgens: quantification by MRI

Microgravity causes rapid decrement in musculoskeletal mass is associated with a marked decrease in circulatory testosterone levels, as we reported in hindlimb-suspended (HLS) rats. In this model which simulates microgravity, we hypothesized that testosterone supplementation should prevent these losses, and we tested this in two studies. Muscle volumes and bone masses were quantitated by using magnetic resonance imaging (MRI) on day 12. In the first study, 12-wk-old Sprague-Dawley rats that were HLS for 12 days lost 28.5% of muscle volume (53.3 +/- 4.8 vs. 74.5 +/- 3.6 cm3 in the ground control rats; P < 0.001) and had a 5% decrease in bone mineral density (BMD) (P < 0.05). In the second study, 30 male 12-wk-old Wistar rats were HLS and were administered either a vehicle (control), testosterone, or nandrolone decanoate (ND). An additional 20 rats were used as ground controls, one-half of which received testosterone. HLS rats had a significant reduction in muscle volume (42.9 +/- 3.0 vs. 56 +/- 1.8 cm3 in ground control rats; P < 0.01). Both testosterone and ND treatments prevented this muscle loss (51.5 +/- 2 and 51.6 +/- 1.2 cm3, respectively; a 63% improvement; P < 0. 05). There were no statistical differences between the two active treatment groups nor with the ground controls. Similarly, there was an 85% improvement in BMD in the testosterone group (1.15 +/- 0.04 vs. 1.04 +/- 0.04 density units in vehicle controls; P < 0.05) and a 76% improvement in the ND group (1.13 +/- 0.07 density units), whereas ground control rats had a BMD of 1.17 +/- 0.03 density units. Because serum testosterone levels are markedly reduced in this model of simulated microgravity, androgen replacement seems to be a rational countermeasure to prevent microgravity-induced musculoskeletal losses.

Monoclonal antibodies reveal expression of the CGRP receptor in Purkinje cells, interneurons and astrocytes of rat cerebellar cortex

The molecular layer of adult rat cerebellum displays high levels of calcitonin gene-related peptide (CGRP) receptors, but the cellular location of the receptor remains unidentified. In an attempt to reveal the expression sites of these receptors, monoclonal antibodies raised against purified CGRP receptors from porcine cerebellar membranes were used in double-immunofluorescence experiments combined with confocal microscopy. PEP-19, a marker that is highly enriched in Purkinje cells (Pc), revealed that CGRP receptors are located in Pc cytoplasm and dendrites, where they label small puncta sometimes arranged in a row along the course of the dendrite itself. CGRP receptors were also located in inhibitory interneurons. Furthermore, as shown by double-labeling experiments with GFAP, CGRP receptor-IR labeled Golgi epithelial cells and their radial fibers (Bergmann fibers), as well as astrocytic processes encircling Pc somata. The simultaneous presence of CGRP receptors in Purkinje cells and in the glial cells that heavily enshroud Purkinje cells allows us to hypothesize that these receptors may be involved in neuron-glia interactions influencing neuronal activity.

Pre-eclamptic toxemia: potential new therapy based on animal studies

OBJECTIVE

Pre-eclamptic toxemia (PET) affects 4 to 8% of human pregnancies. Presently, reliable specific therapies to treat this disorder are not available. This study was designed to develop a new therapeutic approach in the management of PET using an animal model.

DESIGN

Pregnant rats (5/group) infused with 50 mg L-NAME daily via osmotic mini pumps from day 17 of gestation developed a PET-like syndrome. Systolic blood pressure (BP) was monitored daily during pregnancy and up to 7 days postpartum by the tail cuff method. Pup weight and mortality were recorded immediately after delivery. We examined the effect of CGRP to ameliorate L-NAME-induced hypertension during pregnancy, and the efficacy of CGRP and progesterone in combination to inhibit L-NAME-induced hypertension during the post-partum period.

RESULTS

Blood pressure in L-NAME-treated rats was significantly elevated (P < 0.01) throughout pregnancy (141 +/- 3 to 166 +/- 10 mm Hg). CGRP 10 micrograms/day did not cause hypotension, the values being similar to controls which received only saline. On the other hand, CGRP infusion inhibited L-NAME-induced hypertension to normotensive levels (116 +/- 3 to 122 +/- 2) during pregnancy (up to day 22 of gestation), but not during postpartum period (137 +/- 8 to 148 +/- 2). During the post-partum period, neither progesterone nor CGRP by itself was effective in lowering L-NAME-induced hypertension. The combination of CGRP with progesterone decreased BP to control levels in the post-partum period, and also significantly improved foetal mortality and growth (P < 0.05).

CONCLUSIONS

CGRP inhibited L-NAME-induced hypertension during pregnancy and not during postpartum period. The same phenomenon was evident in the presence of adequate levels of progesterone in the post-partum period. We believe that CGRP regulates vascular adaptations during pregnancy and these effects may be progesterone-dependent. This combination treatment of CGRP plus progesterone may be a promising therapy in the management of PET in humans.

Uterine relaxation responses to calcitonin gene-related peptide and calcitonin gene-related peptide receptors decreased during labor in rats

OBJECTIVES

Our purpose was to investigate (1) whether uterine relaxation responses to calcitonin gene-related peptide are differentially regulated during pregnancy and labor, (2) the involvement of nitric oxide in smooth muscle relaxant action of calcitonin gene-related peptide in the rat uterus, (3) whether receptors for calcitonin gene-related peptide are expressed in rat uterus, and if so (4) whether the concentrations of these receptors are differently regulated during pregnancy and labor.

STUDY DESIGN

Rats were killed on day 18 of gestation, at the time of spontaneous labor, or postpartum day 2. The uteri were removed for in vitro contractility measurements, nitric oxide production, and calcitonin gene-related peptide receptor binding assay.

RESULTS

(1) Calcitonin gene-related peptide induced a dose-dependent relaxation in spontaneously contracting uterine strips from pregnant rats on day 18 of gestation; (2) the relaxation effects of calcitonin gene-related peptide on the uterus were decreased during spontaneous delivery at term and post partum compared with that during pregnancy; (3) calcitonin gene-related peptide-induced relaxation was inhibited by pretreatment of the uterine tissue with a calcitonin gene-related peptide receptor antagonist, calcitonin gene-related peptide(8-37); (4) nitric oxide synthesis inhibitor (N(G)-nitro-L-arginine methyl ester) and soluble guanylate cyclase inhibitor (LY83583) significantly decreased calcitonin gene-related peptide-induced relaxation of the rat uterus during pregnancy; (5) calcitonin gene-related peptide increased the uterine nitric oxide production in pregnant rats, and this increase was obliterated in the presence of calcitonin gene-related peptide(8-37); and (6) calcitonin gene-related peptide receptors are present in rat uterus, and the concentration of these receptors dramatically increases during pregnancy and decreases during labor at term.

CONCLUSIONS

Calcitonin gene-related peptide inhibits uterine spontaneous contractions in rats during pregnancy but not during labor and post partum. The inhibitory effects of calcitonin gene-related peptide on uterine contractility appear to be modulated, at least in part, by the activation of nitric oxide generation in the rat uterus. Changes in calcitonin gene-related peptide receptors could contribute to the changes in calcitonin gene-related peptide-mediated uterine relaxation during pregnancy and labor.

Calcitonin Gene-related Peptide (CGRP) is a Mediator of Vascular Adaptations During Hypertension in Pregnancy

Hypertension during pregnancy is a serious obstetrical problem, and the pathophysiology of pre-eclampsia is unclear. Evidence is presented that calcitonin gene-related peptide (CGRP) plays a role in the vascular adaptations that occur during pregnancy. In addition, CGRP might be critical for compensatory vasodilatory changes that occur in response to hypertensive insults during pregnancy, and these compensatory mechanisms might require adequate progesterone activity. Thus, we suggest that an inadequate CGRP-mediated compensatory vasodilatory (adaptative) response may play a role in the pathophysiology of hypertensive disorders during pregnancy.

A four-year randomized controlled trial of hormone replacement and bisphosphonate, alone or in combination, in women with postmenopausal osteoporosis

PURPOSE

Hormone replacement therapy (HRT) with estrogen and treatment with bisphosphonates have been shown to increase bone mineral density (BMD) in postmenopausal women. This 4-year prospective randomized study was carried out to assess the effectiveness of the combined HRT plus etidronate on BMD in postmenopausal women with established osteoporosis.

PATIENTS AND METHODS

Seventy-two postmenopausal women (mean age 64.9+/-0.5 years) attending metabolic bone disease outpatient clinics with established osteoporosis were randomly allocated into one of four treatment groups and monitored for 4 years. All patients enrolled in this study including the control group (n=18) received 1.0 g elemental calcium and 400 units vitamin D per day. The HRT group (n=18) received cyclical estrogen and progesterone; the etidronate group (n=17) received intermittent cyclical etidronate; and the combined therapy group (n=19) received both HRT and etidronate. BMD was measured in the lumbar spine and the hip before treatment and at 2 and 4 years after treatment. Changes in height were recorded, and the occurrence of new vertebral fractures were documented in comparison with the baseline radiographic evaluation. In 40 patients (10 patients per group), analysis of bone histomorphometry was carried out after 4 years of treatment.

RESULTS

In patients who received the combined therapy, BMD increased in the lumbar spine by 10.4% (P <0.001) and in the hip by 7.0% (P <0.001) at 4 years. For patients treated with ICE, these increases were 7.3% (P <0.001) and 0.9% (P <0.05), and with HRT, the increases were 7.0% (P <0.001) and 4.8% (P <0.01) in the vertebrae and femora, respectively. The group treated with calcium and vitamin D lost 2.5% (P <0.05) and 4.4% (P <0.01) of BMD in the vertebrae and femora, respectively, after 4 years. Patients who received combined therapy had significantly higher BMD in both the vertebrae and in the femora (P <0.05) in comparison with patients who were treated with HRT or etidronate alone after 4 years. In comparison with patients in the control group, there was a trend toward a lower rate of new vertebral fractures in the treatment groups. Height loss was significantly less in all three active treatment groups (HRT [P <0.001], etidronate [P <0.02], and combined therapy group [P <0.0001]), in comparison with the control group. The combined therapy group did not have a significant height loss, in comparison with the HRT (P <0.02) and the etidronate (P <0.001) groups. None of the patients had histomorphometric evidence of osteomalacia.

CONCLUSION

This 4-year randomized study showed an additive effect of etidronate and HRT on hip and spine BMD in postmenopausal women with established osteoporosis.

Prevention of corticosteroid-induced bone loss with alendronate

The putitive bone-sparing effect of alendronate was tested in two animal models of osteopenia: estrogen-deficient female rats and glucocorticoid-treated male rats. In the first study, 18 female Sprague-Dawley rats, 4 months of age, were ovariectomized (OVX), and an additional 6 rats were sham-operated. The OVX rats were treated with either vehicle, 17beta-estradiol (E2) (100 microg/rat/week, s.c.), or alendronate (1 mg/kg/day, on alternate days, orally). In the second study, 24 8-month-old male Wistar rats were treated with either vehicle, methyl prednisolone (7 mg/kg once a week, s.c.), prednisolone plus testosterone (16 mg/kg once every 3 weeks, i.m.), or prednisolone plus alendronate (20 microg/kg twice a week, s.c.). Prior to treatment and at the end of the 6-week treatment period, bone mineral density (BMD) of the lumbar spine was measured by dual energy x-ray absorptiometry, and mean femur weights were calculated. The OVX rats had subnormal BMD (-3.91 +/- 1.0% vs control +5.19 +/- 3.92%, P < 0.05) and femur weights (720 +/- 6 mg vs %; 746 +/- 11 mg, P < 0.05). OVX-induced bone loss was completely abolished by the administration of E2 (7.01 +/- 2.32%, P < 0.005; 748 +/- 6 mg, P < 0.01), or alendronate (24.2 +/- 2.73%, P < 0.0001; 779 +/- 11 mg, P < 0.001). In the second study in older male rats, glucocorticoids significantly decreased BMD (-9.70 +/- 3.44% vs -1.10 +/- 1.75%, P < 0.05), and femur weight (1070 +/- 14 mg vs 1180 +/- 24 mg, P < 0.01). Concomitant administration of testosterone (BMD 4.23 +/- 1.84%, P < 0.005; femur weight 1260 +/- 56 mg, P < 0.02), or alendronate (BMD 8.18 +/- 1.36%, P < 0.001; femur weight 1360 +/- 50 mg) with prednisolone, abolished the corticosteroid-induced bone loss. Bone histomorphometry showed a 34% loss of trabecular bone volume in glucocorticoid-treated rats (P < 0.05), which was prevented with both testosterone and alendronate therapies. However, at the doses used in both models, alendronate was more efficacious than either E2 or testosterone in increasing BMD and femur weight. In summary, this study demonstrated that alendronate therapy is highly effective in counteracting the osteopenia of OVX and glucocorticoid therapy.

Prevention of corticosteroid-induced bone loss with nitric oxide donor nitroglycerin in male rats

Nitric oxide (NO) has been reported to inhibit osteoclastic bone resorption. We examined the bone sparing effect of NO on prevention of corticosteroid-induced bone loss in older male rats. Recently, we demonstrated that NO donor nitroglycerin (NG) can alleviate ovariectomy-induced bone loss, and the protective effects of estrogens on bone are mediated through NO [Bone 18(4):301-304; 1996]. Therefore, we chose to study a different model (i.e., steroid-induced osteoporosis in males) to evaluate whether NG can inhibit the bone loss associated with corticosteroid therapy. Twenty-five 32-week-old male Wistar rats were randomly assigned to five groups (n = 5/group). They received either vehicle, methylprednisolone (7 mg/kg per week), NO synthase inhibitor L-NAME (25 mg/kg per day), NO donor nitroglycerin (NG, 0.2 mg twice daily), a combination of prednisolone+NG, or prednisolone plus L-NAME, respectively. Prior to treatment and at the end of the 6 week treatment period, bone mineral density (BMD) of the lumbar spine was measured by dual energy X-ray absorptiometry scanning. Administration of prednisolone significantly decreased BMD (-9.50%, p < 0.05). The group receiving NG with prednisolone (-2.34%) and the group treated with NG alone (-0.36%) were not statistically different from the control group (-0.11%). Similar to the changes in BMD, femur weights were also significantly lower in prednisolone-treated rats (1.09 +/- 0.01 g vs. 1.17 +/- 0.03 in controls; p < 0.05). However, the rats receiving prednisolone together with NG were able to maintain their femur weights (1.13 +/- 0.02). There was a reduction of 9.5% of BMD (p < 0.05) and 7.8% of femoral weight (p < 0.05) in rats treated with L-NAME. A 50%-70% reduction of the percentage trabecular bone volume in the proximal tibia and distal femur and a 50% reduction of the midshaft cortical area was seen after corticosteroid therapy, and these too were prevented by administration of NG. Here, we demonstrate, for the first time, that supplementation with a NO donor compound can counteract prednisolone-induced bone loss.

Progesterone up-regulates vasodilator effects of calcitonin gene-related peptide in N(G)-nitro-L-arginine methyl ester-induced hypertension

OBJECTIVE

We recently reported that calcitonin gene-related peptide can reverse the hypertension produced by N(G)-nitro-L-arginine methyl ester in pregnant rats. In the current study we investigated whether these vasodilator effects of calcitonin gene-related peptide were progesterone dependent.

STUDY DESIGN

Calcitonin gene-related peptide or N(G)-nitro-L-arginine methyl ester was infused through osmotic minipumps, either separately or in combination, to groups of five pregnant rats from day 17 of gestation until day 8 post partum or to nonpregnant ovariectomized rats for 8 days. Progesterone was injected during days 1 to 6 post partum and for 6 days after ovariectomy. Systolic blood pressure was measured daily.

RESULTS

Animals receiving N(G)-nitro-L-arginine methyl ester exhibited significant elevations of blood pressure during pregnancy and post partum. Coadministration of calcitonin gene-related peptide to these rats reversed the hypertension during pregnancy but not during the postpartum period. At the dose used in this study calcitonin gene-related peptide administered alone was without significant effects on blood pressure. However, it reduced both the mortality and growth restriction of the fetus associated with N(G)-nitro-L-arginine methyl ester in these animals. Calcitonin gene-related peptide reversed the hypertension in N(G)-nitro-L-arginine methyl ester-infused postpartum rats during the periods of progesterone treatment only, and these effects were lost when progesterone treatment was stopped. Neither progesterone nor calcitonin gene-related peptide alone were effective. To further confirm these observations, progesterone effects were tested in ovariectomized adult rats. Similar to the findings in postpartum rats, calcitonin gene-related peptide completely reversed the elevation in blood pressure in N(G)-nitro-L-arginine methyl ester-treated rats receiving progesterone injections. The effects of calcitonin gene-related peptide were apparent only during the progesterone treatment period, and these effects were lost when progesterone treatment was stopped. Again, at these doses calcitonin gene-related peptide and progesterone were each ineffective alone.

CONCLUSIONS

Calcitonin gene-related peptide reverses the N(G)-nitro-L-arginine methyl ester-induced hypertension during pregnancy, when progesterone levels are elevated, but not post partum or in ovariectomized nonpregnant rats. The blood pressure-lowering effects of calcitonin gene-related peptide were restored in both postpartum and ovariectomized rats with progesterone treatment. Therefore we conclude that progesterone modulates vasodilator effects of calcitonin gene-related peptide in hypertensive rats.

Calcitonin gene-related peptide is a depressor in NG-nitro-L-arginine methyl ester-induced hypertension during pregnancy

Inhibition of nitric oxide production with NG-nitro-L-arginine methyl ester (L-NAME) increases blood pressure and fetal mortality in pregnant rats. We previously reported that administration of calcitonin gene-related peptide (CGRP) reduces the blood pressure and fetal death produced by L-NAME. To determine the hemodynamic role of endogenous CGRP in this setting, CGRP8-37, a CGRP receptor antagonist, was used. In addition, CGRP mRNA and peptide levels were determined in dorsal root ganglia. L-NAME or control rats had intravenous (for drug administration) and arterial (for continuous mean blood pressure monitoring) catheters surgically placed and were studied in the conscious unrestrained state. Baseline blood pressure was higher in the L-NAME than the control rats on days 19, 20, and 21 or pregnancy and postpartum day 1. Vehicle administration did not change blood pressure in any group, and CGRP8-37 (100 micrograms) did not change blood pressure in control groups. However, CGRP8-37 administration to the L-NAME rats further increased blood pressure (P < .05) on days 19 (8 +/- 1), 20 (12 +/- 2), and 21 (7 +/- 1) of gestation but was without effect on postpartum day 1. Furthermore, CGRP mRNA or peptide levels in dorsal root ganglia were not different between the L-NAME and control rats at any of the time points studied. These data indicate that in experimental preeclampsia, CGRP is playing a compensatory vasodilator role to attenuate the elevated blood pressure. The mechanism of this effect appears to be an enhanced vascular responsiveness to CGRP that is attenuated after the birth of pups.

Amylin, calcitonin gene-related peptide, calcitonin, and adrenomedullin: a peptide superfamily

The calcitonin gene peptide superfamily consists of calcitonin (CT), calcitonin gene-related peptide (CGRP), and amylin. CT and CGRP derive from the CT/CGRP gene, which is encoded on chromosome 11. Alternative splicing of the primary RNA transcript leads to the translation of CGRP and CT peptides in a tissue-specific manner. CGRP (a 37-amino-acid neuropeptide) and its receptors are widely distributed in the body, and it is the most potent endogenous vasodilatory peptide discovered so far. CT (a 32-amino-acid peptide) is, however, a hormone primarily involved in protecting the skeleton during periods of "calcium stress" such as growth, pregnancy, and lactation. CT derives from the C cells of the thyroid gland and is the most potent peptide inhibitor of osteoclast-mediated bone resorption. Therefore, treatment with CT is highly effective for conditions associated with increased bone turnover such as Paget's disease, osteoporosis, Sudeck's atrophy, and hypercalcemia. Amylin (a 37-amino-acid peptide) is generated from a gene located on chromosome 12 (thought to be an evolutionary duplication of chromosome 11) and shares 46% amino acid sequence homology with CGRP and 20% with human CT. Amylin is predominantly located in the beta cells of the islets of the pancreas and may be involved in the pathogenesis of type II diabetes by deposition as amyloid within the pancreas, leading to beta cell destruction. Adrenomedullin, a recently discovered 52-amino-acid vasoactive peptide from adrenal tissue, shares 24% homology with CGRP and is also a member of this superfamily of peptides. A portion of the B-chain of insulin is strongly homologous to these four peptides. Not only does adrenomedullin (13-52) show 24% amino acid homology with CGRP, it also has a biological activity profile similar to that of CGRP.CGRP, CT, and amylin are related to the insulin gene superfamily of peptides, which may all have diverged from a common ancestral gene during evolution. When the crystallographic- and nuclear magnetic resonance-based molecular modeling of the three-dimensional structure of CGRP, CT, amylin, and adrenomedullin peptides and their receptors is available, it will lead to a greater understanding of the involvement of this family of peptides in pathophysiology. Together, CGRP, CT, amylin and adrenomedullin have overlapping biological effects owing to their structures and cross-reactivity between receptors. I propose that CT, CGRP, adrenomedullin, and amylin belong to a family of G-protein-coupled receptors (an "insulin superfamily" of peptides) and therefore share some of the characteristics of insulin, such as growth factor-like effects, and possible interaction at insulin receptor sites as an antagonist.

Calcitonin gene-related peptide reverses the hypertension and significantly decreases the fetal mortality in pre-eclampsia rats induced by N(G)-nitro-L-arginine methyl ester

We recently established that the chronic inhibition of nitric oxide production with N(G)-nitro-L-arginine methyl ester (L-NAME) increases blood pressure and fetal mortality in pregnant rats. Using this animal model, we have investigated whether calcitonin gene-related peptide (CGRP) can reverse the pre-eclampsia-like conditions produced by L-NAME. CGRP and L-NAME were chronically infused s.c. into pregnant rats separately or together starting on day 17 of gestation; a control group was given saline infusions. Systolic blood pressure was measured on gestational days 17, 18, 19 and 22 and post-partum days 1 and 2. The weight and mortality of the pups were recorded immediately after spontaneous delivery. Animals treated with L-NAME exhibited significant elevations of blood pressure on days 18, 19 and 22 of gestation and during post-partum, increased pup mortality (18.4 versus 0.0%) and decreased pup weights (5.14 +/- 0.07 versus 6.20 +/- 0.06 g). The co-administration of L-NAME and CGRP prevented the gestational (not the post-partum) L-NAME hypertension and decreased pup mortality to 6.4% but did not reverse the decreased fetal weight (5.31 +/- 0.06 g). Our data indicate the CGRP (i) participates in regulation of the vascular adaptations that occur during normal pregnancy, (ii) has beneficial effects on the hypertension and increased mortality of experimental preeclampsia, and (iii) may exert differential effects on the systemic (i.e. maternal) and fetal components of utero-placental circulation. These findings may have important clinical implications.

Nitric oxide donor alleviates ovariectomy-induced bone loss

Nitric oxide (NO) has been reported to inhibit osteoclastic bone resorption. We examined the bone-sparing effect of NO after 6 weeks of administration into estrogen-deficient rats. 30 female Sprague-Dawley rats, 12 weeks of age, underwent ovariectomy (OVX), and 5 rats were sham-operated. OVX rats were assigned to six groups (n = 5/group) treated respectively with: vehicle; 17-beta-estradiol (E2); nitroglycerine (NG, NO donor); NG-nitro-L-arginine methyl ester (L-NAME, NO synthase inhibitor); combination of E2 + NG; and a combination of E2 + L-NAME. Prior to treatment and at the end of the treatment period, bone mineral density (BMD) of rats was measured by dual-energy X-ray absorptiometry (DXA) scanning. OVX animals had significantly lower BMD and femur weights in comparison to sham operated rats (p < 0.01), and this was completely prevented by the administration of E2 (p < 0.01). Administration of NG alone prevented OVX-induced bone loss (p < 0.05). The combination of E2 + NG did not further enhance the bone mass or femur weight, and the OVX-induced bone loss was not further aggravated by L-NAME. However, in the presence of L-NAME, E2 was totally ineffective in reversing the bone loss, suggesting that the protective effect of estrogens against bone loss may be mediated through NO. In summary, the results suggest that NO counteracts the bone loss associated with OVX.

Amylin-immunoreactivity is co-stored in a serotonin cell subpopulation of the vertebrate stomach and duodenum

Amylin (or islet amyloid polypeptide) is a 37 amino acid peptide originally isolated from amyloid deposits in the pancreas of non-insulin dependent diabetic patients. It has already been immunohistochemically localised within the B and D cells of pancreatic islets and in endocrine cells of the rat and human stomach and duodenum. In this phylogenetic study, a polyclonal antiserum raised against the carboxy-terminal tridecapeptide amide of human amylin was used to demonstrate and examine the distribution of amylin-immunoreactivity in the stomach and duodenum of various vertebrate species. Except for fish, gastrointestinal tracts of all the species studied contained amylin-immunoreactive endocrine cells. They were located chiefly in the lower half portion of the distal gastric body and pyloric glands, and in the lining epithelium of the duodenal villi and crypts. Many cells were elongated, triangular or oval, and had a cytoplasmic process that extended from the cell base along the basement membrane. Others had a bipolar feature that gave them a so-called "open" appearance. Double and triple staining procedures on the same tissue section showed that almost all the amylin-immunoreactive cells present in the gastroduodenal region also co-stored serotonin and chromogranin A, and displayed argyrophilia in Grimelius impregnation. On the other hand, almost all the serotonin-immunoreactive cells of this region co-stored amylin, whereas those in more distal gut regions did not. This finding suggests that those amylin-containing cells correspond to a subtype of gastroduodenal serotonin cells.

Purification and biochemical characterization of neuropeptide Y2 receptor

Neuropeptide Y (NPY) receptors consist of three subtypes, designated NPY1, NPY2, and NPY3. The Y1 receptor has been cloned. The present study reports the purification of the NPY-Y2 receptor from porcine brain and its biochemical characterization. NPY receptors were solubilized and purified by sequential hydrophobic interaction, ion exchange, and NPY-affinity chromatography. By use of SDS-polyacrylamide gel electrophoresis, high performance liquid chromatography gel permeation chromatography, and chemical cross-linking studies, the affinity-purified brain NPY-Y2 receptor was identified as a monomeric glycoprotein with a molecular mass of 60 kDa. Following deglycosylation, the molecular mass of the Y2 receptor was decreased to 45 kDa. Although the 125I-NPY binding to the purified NPY receptor was considerably decreased by N-ethylmaleimide, guanine nucleotides had no effect. Therefore, the purified NPY-Y2 receptor is probably not associated with G-proteins, but may have intramolecular-free sulfhydryl groups. The specific activity of the isolated NPY-Y2 receptor is 15.8 nmol/mg of protein. The isolated receptor retained its capacity to bind to 125I-NPY, specific to NPY and peptide YY, and showed no cross-reactivity with any other peptides. Highly purified (10(9)-fold purification) NPY receptor from the brain was identified as the Y2 subtype as demonstrated by its affinity to C-terminal fragments of NPY, including NPY-(13-36).

Mechanisms of the antihypertensive effects of dietary calcium and role of calcitonin gene related peptide in hypertension

Alterations in calcium metabolism and calcium-regulating hormones have been described in essential hypertension. However, the mechanisms that mediate these responses are unknown. In previous studies, using the genetically spontaneously hypertensive rat and the mineralocorticoid-salt (DOC-salt) hypertensive rat model, we and others have observed that oral calcium supplementation attenuates the associated increase in peripheral vascular resistance and consequently lowers blood pressure (BP). When hypertensive patients (n = 8, diastolic BP 90-95 mmHg (1 mmHg = 133.3 Pa)) were given daily oral calcium supplementation (1.4 g elemental calcium), both systolic and diastolic BP were decreased (5-10 mmHg, p < 0.01). The only biochemical variables significantly changed were serum ionized calcium and intact parathyroid hormone (PTH, 1-84) (p < 0.05); furthermore, the levels of calcitonin gene related peptide (CGRP), measured by both radioimmunoassay and radioreceptor assay, showed a marked 75% increase (p < 0.001). The antihypertensive effects of Ca2+ and the increased levels of CGRP in the circulation returned to baseline levels immediately following cessation of calcium supplementation, suggesting that the effects of calcium on BP and CGRP are specific. On the basis of these observations were proposed that the antihypertensive effect of dietary calcium supplementation, at least in part, is mediated through CGRP.

Combined therapy with estrogen and etidronate has an additive effect on bone mineral density in the hip and vertebrae: four-year randomized study

BACKGROUND

Administration of estrogen or etidronate has been shown to increase bone mineral density in postmenopausal women. This 4-year, prospective, randomized study was carried out to monitor any added beneficial effect on bone mineral density when hormone-replacement therapy (HRT) was combined with etidronate.

PATIENTS AND METHODS

Fifty-eight early postmenopausal women attending metabolic bone disease outpatient clinics were randomly allocated into four treatment groups and monitored for up to 4 years. All patients received 1.0 g/d of elemental calcium. In addition, group 1 received percutaneously administered HRT (n = 15); group 2, intermittent cyclical etidronate (ICE) (n = 14); group 3, HRT and ICE (n = 15); and group 4, calcium alone (n = 14). The bone mineral density (measured by dual-energy x-ray absorptiometry), biochemical variables of bone turnover, including bone-specific alkaline phosphatase, and urinary hydroxyproline:creatinine ratios were measured before treatment and at 2 and 4 years after treatment.

RESULTS

In patients who received the combined therapy, bone mineral density was increased in the vertebrae by 10.9% (P < 0.001) and in the femora by 7.25% (P < 0.001) at 4 years. For patients treated with ICE, the increase was 6.79% (P < 0.001) and 1.20% (P < 0.05), and with HRT, 6.78% (P < 0.001) and 4.01% (P < 0.01) in the vertebrae and femora, respectively. The group treated with calcium alone lost 3.81% (P < 0.01) and 4.96% (P < 0.01) of bone mineral density in vertebrae and femora. Patients who received no specific therapy lost 8.58% (P < 0.01) from vertebrae, and 7.83% (P < 0.01) from the femora over 4 years. Patients who received combined therapy had significantly higher bone mineral density in both vertebrae (P < 0.05) and femora (P < 0.01), in comparison to patients who were treated with HRT, or ICE, alone. Three of 9 patients (33%) in the ICE group developed osteomalacia, as shown by bone histomorphometry, whereas in women who received combined HRT and ICE therapies, none of the 11 patients tested had evidence of bone mineralization defects.

CONCLUSION

This 4-year, prospective, randomized study in early postmenopausal women showed an additive effect of ICE and HRT on the bone mineral density in both vertebrae and the hip. Furthermore, the combined therapy prevented the occurrence of osteomalacia associated with etidronate. This is the first study to demonstrate the effects of etidronate in early postmenopausal women, and the additive beneficial effects of HRT and ICE on bone mineral density.

Comparative immunohistochemical distribution of amylin-like and calcitonin gene related peptide like immunoreactivity in the rat central nervous system

Using the indirect immunofluorescence method with a polyclonal antiserum raised in rabbits and directed against amylin (AMY), we have investigated the distribution of AMY-like immunoreactivity (-ir) throughout the central nervous system of the rat. The widespread distribution of AMY-ir was much more abundant than that previously reported for calcitonin gene related peptide (CGRP) immunoreactivity. In most brain areas there was no overlap between AMY- and CGRP-ir cell body groupings, with the exception of the motor nuclei of the hindbrain and spinal cord, which were found to contain large numbers of AMY- and CGRP-immunoreactive cell bodies. Areas with a moderate to dense appearance of AMY-ir were the rhinencephalon, the nucleus of the diagonal band, the magnocellular, dorso- and ventro-medial and mammillary nuclei of the hypothalamus, the habenula, the compact part of the substantia nigra, the ruber and pontine nuclei, and the inferior olive and the cerebellar nuclei. The widespread immunohistochemical distribution of AMY-ir in the rat brain is in partial agreement with the distribution of AMY-binding sites.

In vivo central actions of rat amylin

The purpose of the present study was to examine and compare the profile of neurobehavioral effects of rat amylin (r-amylin) and rat calcitonin gene-related peptide (rCGRP), two peptides having a 50% structural homology. The effects of synthetic r-amylin and rCGRP administered in several doses (0.312-80.0 micrograms) into the lateral cerebro-ventricle of rats on spontaneous activity, muscular tone, body temperature, nociception, food intake as well as their potential for inducing catalepsy, were investigated. Intraventricular administration of r-amylin or rCGRP significantly reduced spontaneous motor activity and markedly increased body temperature of animals in a dose-dependent related fashion. rCGRP produced a significant increase in muscular tone and induced cataleptic effect in animals, but r-amylin had no effect on these variables. Furthermore, neither r-amylin nor rCGRP were able to induce any significant effect on nociceptive response time of animals in the tail immersion test even with doses as large as 80.0 micrograms. Finally, the two peptides did not affect ad libitum food intake, but significantly reduced food consumption in 22 h food-deprived animals. Together, the results of the present study suggest that amylin may be involved in a diversity of neurophysiological processes but displays a different profile of neurobehavioral effects to that of CGRP which may involve different receptors.

Validation, role in perioperative assessment, and clinical applications of an immunoradiometric assay for human calcitonin

We have evaluated a new immunoradiometric assay (IRMA) for calcitonin (CT) (Medgenix, Belgium). The detection limit of immunoreactive CT (IR-CT) was 2.8 pg/ml, and plasma levels of IR-CT of 134 healthy adults (dynamic range, 2.8-1000 pg/ml) were < 19 pg/ml (median 4.1 pg/ml). Both basal and pentagastrin-stimulated IR-CT levels were < 30 pg/ml and were well separated from the levels in patients with medullary thyroid carcinoma (MTC) (46-29,000 pg/ml, n = 38). In preoperative plasma samples in five patients with C-cell hyperplasia, CT IRMA confirmed the diagnosis, although in two patients RIA failed to detect a significant increase of IR-CT. By modifying the IRMA, we could identify residual tumor tissues perioperatively in patients undergoing thyroidectomy for MTC. RIA of gel-permeation chromatography showed four IR-CT peaks, but IRMA had only three peaks, suggesting that IRMA is more specific. CT-IRMA is more specific, sensitive, robust, rapid, and reliable than RIA. In addition, neat plasma can be used directly in a single step in CT-IRMA.

Optimal frequency of administration of pamidronate in patients with hypercalcaemia of malignancy

OBJECTIVE

Hypercalcaemia of malignancy (HM) is a common metabolic complication associated with cancer. The hypocalcaemic effects of medications used to reduce serum calcium levels in HM are short lived and relapse in hypercalcaemia is not uncommon. Pamidronate is one of the most commonly used bisphosphonates in the treatment of HM but there are no specific guidelines for the frequency of use of this drug in recurrent hypercalcaemia. This study was conducted to assess the optimum frequency of pamidronate therapy necessary to maintain normocalcaemia in patients with HM.

DESIGN AND PATIENTS

Thirty-four patients with HM were randomly allocated into two groups and treated with intravenous pamidronate administered every 14th or 21st day for 16 weeks (n = 17 each group). Serum calcium and urinary hydroxyproline creatinine ratio were measured at weekly intervals.

RESULTS

The calcium-lowering effect of pamidronate was apparent by 48 hours and normocalcaemia was maintained for an average of 15 days. When the drug was administered every 3 weeks, hypercalcaemia and associated symptoms developed in 50% of patients (22 separate episodes) during the 3rd week, before the next dose of pamidronate. The incidence of symptomatic hypercalcaemia was significantly decreased (10%, 8 separate episodes, P < 0.01) and survival was improved (P < 0.05) in patients who received pamidronate every 2nd week, thereby minimizing the unpleasant and potentially dangerous effects of hypercalcaemia.

CONCLUSIONS

Intravenous pamidronate 60 mg/dose, administered every two weeks, can maintain normocalcaemia in the vast majority of patients with hypercalcaemia of malignancy.

Significance of plasma PTH-rp in patients with hypercalcemia of malignancy treated with bisphosphonate

BACKGROUND

Hypercalcemia of malignancy (HM) is one of the commonest metabolic complications associated with cancer. Plasma parathyroid hormone-related peptide (PTH-rp) is known to cause hypercalcemia in the vast majority of patients with HM.

METHODS

Fifty-two patients with HM were treated with a single infusion of 60 mg of pamidronate (3-amino-1-hydroxypropylidene-1, 1-bisphosphonate). Serum calcium and plasma PTH-rp levels were measured at the basal and after pamidronate therapy.

RESULTS

Normocalcemia was achieved in 43 (i.e., 83%) of these patients within 3 to 5 days. Eighty-one percent had increased plasma PTH-rp levels. There was no difference in the percentages of patients who had elevated plasma PTH-rp levels compared with those of patients with metastatic bone disease and humoral HM. However, the latter group of patients had significantly higher circulatory PTH-rp levels (P < 0.01). The pretreatment calcium levels were not correlated with the calcium-lowering responses nor with plasma PTH-rp levels. However, there was a significant positive correlation between pretreatment plasma PTH-rp levels and the nadir serum calcium (P < 0.001) and a negative correlation with the changes in serum calcium levels (P < 0.001) after pamidronate therapy. No relationship existed between pretreatment calcium levels or PTH-rp levels with the extent or the severity of the metastatic bone disease. Patients who had the highest PTH-rp levels had the worst prognosis, poorest calcium-lowering effect, shortest duration of normocalcemia, and required higher doses and frequent infusions of pamidronate to maintain normocalcemia. The nonresponders to therapy had a significantly higher mean plasma PTH-rp level (> 75 pg/ml) than the responders (P < 0.01).

CONCLUSIONS

The plasma PTH-rp levels may help to predict the calcium-lowering effect of bisphosphonate and give an indication of the prognosis in patients with HM. They may allow identification of patients who need higher doses and increased frequency of administration of bisphosphonate, thereby expediting the normocalcemic response.