Degradation of cell surface heparan sulfates decreases the high affinity binding of basic FGF to endothelial cells, but not to FRTL-5 rat thyroid cells

The role of cell surface heparan sulfate proteoglycans in the effect of basic fibroblast growth factor (bFGF) on FRTL-5 rat thyroid cells was investigated and compared with that of endothelial cells. FRTL-5 cells were incubated for 2 h with heparitinase (0.5-5.0 mU/mL), which specifically degrades heparan sulfate proteolgycans, and then stimulated by bFGF. The mitogenic effect of bFGF was estimated by measuring [3H]thymidine incorporation. Although cell surface heparan sulfates have been believed to be necessary for bFGF binding to its high affinity receptors, the heparitinase treatment had no significant effect on the DNA synthesis of FRTL-5 cells stimulated by bFGF. The binding study revealed that heparitinase treatment decreased low affinity bindings of [125I]bFGF to FRTL-5 cells by only 50% and did not attenuate the high affinity binding, while the same treatment abolished the high and low affinity binding to bovine pulmonary artery endothelial (CPAE) cells. Analysis of trypsin accessible cell surface 35SO4-labeled materials by Q-sepharose anion-exchange column chromatography showed that heparan sulfate proteoglycans, peaked at 0.55 M NaCl elution, disappeared from the surface of FRTL-5 cells after treatment with 2.0 mU/mL of heparitinase, indicating that the heparitinase resistant low-affinity binding sites are not heparan sulfates. These results demonstrate that cell surface heparan sulfates are not required for the high affinity binding of bFGF to FRTL-5 rat thyroid cells, while proteoglycans are necessary for binding to endothelial cells, and suggest that the mechanism of the action of bFGF is different in rat thyroid cells compared with endothelial cells.

Potential of the histoculture drug-response assay to contribute to cancer patient survival

The histoculture drug-response assay (HDRA) was recently evaluated in a retrospective clinical trial and was found to correlate to drug sensitivity, resistance, and patient survival. To further investigate the potential of HDRA to contribute to patient survival, 215 patients with gastric cancer from 45 medical centers were tested with the HDRA in a blinded study after resection of the primary lesion. One hundred sixty-eight patients received at least 20 mg/m2 of mitomycin C and a minimum of 30 g UFT, a mixture of tegafur and uracil at a molar ratio of 1:4, thereby making them eligible for the study. Of these cases 128 were evaluable by the HDRA. The evaluable patient tumors were tested by the HDRA with the [3H]thymidine incorporation end point measured by microautoradiography to be drug "sensitive" or "resistant." The in vitro conditions for distinguishing sensitivity and resistance that matched the response rates for historical controls for gastric carcinoma were 90% inhibition rate and 0.12 microgram/ml for mitomycin C and 70% inhibition rate and 1 microgram/ml for 5-fluorouracil, respectively. Most importantly in the blinded study, the overall and disease-free survival rates of the HDRA-sensitive group were found to be significantly higher than those of the HDRA-resistant group tested under the above conditions. The data further indicate the importance of three-dimensional tumor culture for obtaining accurate clinical information. The results demonstrate that the HDRA response correlates to patient survival, which suggests the potential of the HDRA to contribute to patient survival in gastric cancer when used prospectively.

Gene expression of vascular natriuretic peptide receptor in the aorta of hypertensive rats

1. To elucidate the pathophysiologic role of vascular natriuretic peptide (NP) receptor in hypertension, we determined NP-A and NP-B receptor mRNA levels by means of ribonuclease protection assay in aorta of three types of hypertensive rats. 2. The NP-A receptor mRNA level was higher in stroke-prone spontaneously hypertensive rats (SHR-SP/Izm) and deoxycorticosterone acetate-salt hypertensive rats than that in their respective control rats. On the contrary, the NP-A receptor mRNA level was lower in NG-nitro-L-arginine-methyl ester (L-NAME)-induced hypertensive rats compared with that in the control. 3. The NP-B receptor mRNA level did not show any significant change in all three hypertensive rats compared with their respective controls. 4. The present study suggests that high blood pressure is not the major factor regulating the NP receptor gene expression and also that the receptor subtype is independently regulated from each other.

Sexually dimorphic expression of pituitary growth hormone-releasing factor receptor in the rat

Secretion of growth hormone (GH) exhibits marked sexual dimorphism in the rat. To examine the underlying mechanism that involves hypothalamic GH-releasing factor (GRF), we determined pituitary GRF receptor mRNA levels in male and female rats and compared their in vitro abilities to release GRF, an endogenous ligand for GRF receptor. Female rats expressed GRF receptor mRNA at a level of only 15% (P < 0.001) of that of male rats. Female rats also showed a 33% lower (P < 0.01) ability to release GRF than male rats. These results indicate that the GRF secretion and action system of female rats is characterized by the combined reduction in GRF receptor expression and GRF-releasing capacity compared with that of male rats. This could explain the in vivo finding that spontaneous, GRF-triggered GH pulses are of much lower amplitude in the female than in the male rat.

Differential gene expression of vascular natriuretic peptide receptor subtype in artery and vein

Although the vasorelaxation by natriuretic peptide (NP) is much less potent in the vein than in the artery, mechanism underlying the phenomenon remains unknown. Since NP receptor consists of three subtypes with different functions, we determined the mRNA level of each NP receptor subtype in the artery and vein by ribonuclease protection assay. In the aorta, NP-A receptor related to the biological action of NP was the predominant form. By contrast, NP-C receptor related mainly to the clearance of NP was the predominant form in the inferior vena cava: NP-C mRNA level was about two fold higher than in the aorta, while both NP-A and NP-B receptor mRNA levels were about half of that in the aorta. These results provide the molecular basis for the different biological response to NP in the artery and vein. Differential gene expression of NP receptor subtype could be an important determinant of the biological actions of NP.

Effect of acetylcholine on corticotropin-releasing factor gene expression in the hypothalamic paraventricular nucleus of conscious rats

To examine the physiological role of cholinergic input in the regulation of CRF neurons in the paraventricular nucleus (PVN) of the hypothalamus, acetylcholine (ACh) was microinjected bilaterally into the dorsolateral border of the PVN of conscious rats. Changes in the levels of POMC messenger RNA (mRNA) in the anterior pituitary, CRF mRNA in hypothalamic tissue containing the PVN, and plasma ACTH were assessed. Plasma ACTH concentrations increased in a dose-dependent manner after ACh injection (1-100 pmol/side), reaching a peak 30 min after ACh injection and returning to baseline within 120 min. The POMC mRNA level in the anterior pituitary and the hypothalamic CRF mRNA level increased in a dose-dependent manner 120 min after ACh (0.1-10 pmol/side) injection. Intracerebroventricular pretreatment with atropine completely abolished the ACh-induced increase in plasma ACTH concentrations, whereas pretreatment with hexamethonium was without significant effect. The intracerebroventricular injection of ACh also increased plasma ACTH concentrations in a dose-dependent manner in conscious rats, but not in pentobarbital-anesthetized animals. Thus, cholinergic hypothalamic input stimulates CRF gene expression in the PVN and CRF secretion into the portal circulation under physiological conditions. The use of conscious animals is essential in elucidating the physiological roles of neurotransmitters and other modulators regulating CRF neurons.

Chlordiazepoxide attenuates stress-induced activation of neurons, corticotropin-releasing factor (CRF) gene transcription and CRF biosynthesis in the paraventricular nucleus (PVN)

Corticotropin-releasing factor (CRF) plays a role in coordinating endocrine, autonomic, and behavioral responses to stressful stimuli. Benzodiazepines exert many effects which oppose those of CRF, including anxiolysis and suppression of the pituitary-adrenal axis. In the present study, we employed in situ analysis of CRF heteronucleous RNA (hnRNA) and c-fos mRNA to assess stimulus-induced CRF gene transcription rate following stress and its modulation by chlordiazepoxide (CDP). Male albino rats were exposed to restraint stress for 30 min and sacrificed 30 and 120 min after the onset of stress. Either CDP or vehicle was given intraperitoneally 60 min before stress. To determine plasma ACTH levels by immunoradiometric assay, another group of rats was decapitated 10 min after the onset of restraint stress. Restraint stress induced rapidly and significantly c-fos mRNA and CRF hnRNA expression in the PVN at the 30 min time point. Increases in both RNA copies were significantly inhibited by administration of CDP at doses of 5 and 10 mg/kg. CRF mRNA concentrations were increased significantly in the PVN 120 min after stress and again, CDP attenuated significantly these increases in the PVN. The plasma ACTH increase in response to stress was inhibited significantly by CDP administration at every dose tested. CDP did not change CRF mRNA levels in the non-stressed animal.(ABSTRACT TRUNCATED AT 250 WORDS)

Stimulation by thyroid-stimulating hormone and Grave's immunoglobulin G of vascular endothelial growth factor mRNA expression in human thyroid follicles in vitro and flt mRNA expression in the rat thyroid in vivo

To elucidate the pathogenesis of thyroid gland hypervascularity in patients with Graves' disease, we studied the expression of mRNAs for vascular endothelial growth factor (VEGF) and its receptor, Flt family, using human thyroid follicles in vitro and thiouracil-fed rats in vivo. Human thyroid follicles, cultured in the absence of endothelial cells, secreted de novo-synthesized thyroid hormone in response to thyroid-stimulating hormone (TSH) and Graves' IgG. The thyroid follicles produced VEGF mRNA but not flt-1 mRNA. The expression of VEGF mRNA was enhanced by insulin, tumor-promoting phorbol ester, calcium ionophore, dibutyryl cAMP, TSH, and Graves' IgG. When rats were fed thiouracil for 4 wk, their serum levels of TSH were increased at day 3. VEGF mRNA was also increased on day 3, accompanied by an increase in flt family (flt-1 and KDR/ flk-1) mRNA expression. These in vitro and in vivo findings suggest that VEGF is produced by thyroid follicles in response to stimulators of TSH receptors, via the protein kinase A and C pathways. VEGF, a secretable angiogenesis factor, subsequently stimulates Flt receptors on endothelial cells in a paracrine manner, leading to their proliferation and producing hypervascularity of the thyroid gland, as seen in patients with Graves' disease.

Intracerebroventricular administration of neuropeptide Y inhibits release of noradrenaline in the hypothalamic paraventricular nucleus caused by manual restraint in the rat through an opioid system

Intracerebroventricular injection of 1.5 micrograms neuropeptide Y (NPY) had no effect on basal release of noradrenaline (NA) in the hypothalamic paraventricular nucleus (PVN), measured by intracerebral microdialysis in the rat. However, it blocked the increase in NA release caused by manual restraint but not that by tail-pinch, and the effect was blocked by naloxone (1.0 mg/kg body weight). Thus, NPY attenuates NA release in the PVN by a painless stressor, such as manual restraint, through an opioid system.

Lysine vasopressin stimulation of cortisol secretion in patients with adrenocorticotropin-independent macronodular adrenal hyperplasia

We present two patients with Cushing's syndrome due to ACTH-independent macronodular adrenal hyperplasia who showed marked plasma cortisol response to lysine-8-vasopressin (LVP) injection (from 930 and 731 pmol/L to 2177 and 1920 pmol/L, respectively), while plasma ACTH levels remained undetectable. The ACTH independence of cortisol secretion in the two patients was determined from the following endocrinological findings. Plasma cortisol levels were not increased by corticotropin-releasing hormone injections and were not suppressed by high dose (16 mg) dexamethasone administrations. The plasma ACTH levels, measured by two independent sensitive immunoassays, were persistently undetectable even after corticotropin-releasing hormone injection, metyrapone administration, and bilateral adrenalectomy. The particular pathological finding of the two cases, atrophic lesions in nonnodular parts of the adrenal cortexes, also indicated ACTH independence of the macronodular hyperplasia. In vitro examination revealed a direct effect of LVP on cortisol secretion from the adrenal cells of the macronodules. We also examined seven patients with Cushing's syndrome caused by adrenal adenoma and found a statistically significant plasma cortisol response to LVP injection. The direct effect of LVP was also demonstrated in cultured adenoma cells. In conclusion, we discovered a direct adrenal effect of LVP on cortisol secretion in patients with ACTH-independent macronodular hyperplasia and, to a lesser extent, in patients with cortisol-producing adrenal adenoma. The cortisol response to LVP may serve to facilitate their diagnosis and choice of therapy.

Characteristics of aldosterone-producing adenoma responsive to upright posture

A small subgroup of primary aldosteronism due to aldosteronoma, named aldosterone-producing renin-responsive adenoma (AP-RA), has been reported to masquerade as idiopathic hyperaldosteronism (IHA) because of the responsiveness of the plasma aldosterone concentration (PAC) to upright posture (UP). We found two patients with AP-RA in 19 patients with aldosteronoma who were examined by UP stimulation and were treated surgically. In 17 patients with typical aldosterone-producing adenoma (APA), PAC decreased or increased only slightly (less than 200% of the basal level); in contrast, it increased to over 300% of the basal level in two patients with AP-RA. The two groups were comparatively studied as to their hormonal levels, adrenal computed tomography (CT) scan and histological findings in order to clarify the characteristics of AP-RA. Basal PAC was within the normal range (11.1 and 13.0 ng/dl) in AP-RA but in APA it ranged from 14.8 to 58.1 ng/dl with a mean of 32.3 +/- 2.7 ng/dl. The diameters of the adenoma in AP-RA were apparently smaller (6 and 9 mm) than those in APA ranged from 10 to 25 mm with a mean of 15.5 +/- 1.1 mm. After a contrast medium was injected at CT scan, the density of the normal adrenal gland adjacent to the adenoma increased but that of the adenoma did not in APA, making a clear distinction between the adenoma and the gland. On the other hand, the density of the adenoma and gland increased to almost the same degree in AP-RA.(ABSTRACT TRUNCATED AT 250 WORDS)

Stress-induced activation of neuronal activity and corticotropin-releasing factor gene expression in the paraventricular nucleus is modulated by glucocorticoids in rats

Intronic in situ hybridization methodology provides a means of determining the rate of gene transcription under basal and stimulated conditions. In the present study, we have used intronic in situ hybridization to the corticotropin-releasing factor (CRF) gene to measure hypothalamic CRF gene transcription after stress as well as its modulation by glucocorticoids. Using this and conventional exonic in situ hybridization we examined the time course of changes in c-fos mRNA, and CRF heteronuclear RNA (hnRNA) and mRNA concentrations in the paraventricular nucleus (PVN) of male Wistar rats after restraint stress. In addition, we determined the effects of adrenalectomy and dexamethasone administration on c-fos and CRF gene expression in the PVN. Restraint stress induced a rapid induction (within 5 min) of c-fos mRNA and CRF hnRNA expression in the PVN. Both RNA concentrations peaked at 30 min then decreased and were undetectable 2 h after stress onset. In contrast, the concentration of CRF mRNA increased gradually and a significant elevation was first detected 60 min after the beginning of stress. Adrenalectomy augmented and dexamethasone pretreatment inhibited c-fos mRNA, CRF hnRNA, and mRNA induction after stress. The data suggest that stress-induced activation of neurons, CRF gene transcription, and CRF synthesis in the PVN are modulated by glucocorticoids.

Insulin resistance is associated with high plasma ouabain-like immunoreactivity concentration in NIDDM

The aim of the present study was to elucidate the pathophysiologic significance of circulating ouabain as a link between insulin resistance (IR) and hypertension (HT) in NIDDM. Euglycaemic (4.5 mmol/l) hyperinsulinaemic (360-580 pmol/l) clamping was performed using an artificial endocrine pancreas. Plasma ouabain-like immunoreactivity (OLI) was determined by radioimmunoassay using a highly specific antibody to ouabain. HT was defined as systolic blood pressure > 140 mm Hg and/or diastolic > 90 mm Hg or being treated with antihypertensive agents. The values (mean +/- SEM) of glucose infusion rate (GIR) and plasma OLI were compared among the four groups classified using IR and HT as factors. Group I (IR-/HT-, n = 15): GIR 7.20 +/- 0.36 mg.kg-1.min-1, OLI 130.8 +/- 20.9 pmol/l, which was not different from that in eight normal control subjects (7.69 +/- 0.40 mg.kg-1.min-1 and 142.6 +/- 32.3 pmol/l, respectively); Group II (IR-/HT+, n = 13): 5.89 +/- 0.36 mg.kg-1.min-1, 172.5 +/- 35.0 pmol/l; Group III (IR+/HT-, n = 14) 1.91 +/- 0.28 mg.kg-1.min-1, 576.6 +/- 161.5 pmol/l (p < 0.01 vs Group I and II); Group IV (IR+/HT+, n = 15) 1.79 +/- 0.22 mg.kg-1.min-1, 703.1 +/- 170.1 pmol/l (p < 0.01 vs Group I and II), respectively. Six of 57 NIDDM patients studied exhibited very high (> 1500 pmol/l) plasma OLI concentrations, showed marked insulin resistance and were all hypertensive. When analysed as a whole, plasma OLI was negatively correlated with GIR (p < 0.001), but was not correlated with arterial blood pressure.(ABSTRACT TRUNCATED AT 250 WORDS)

Daily excretion levels of an unidentified ketosteroid in the urine of patients with Cushing's syndrome and healthy subjects measured by a new method

We developed a new method for measuring an unidentified ketosteroid glucuronide (US-G) detected by the method of Iwata et al. for measuring 17-ketosteroid glucuronides by reversed phase HPLC on a Capcell-Pak C8 column with three kinds of mobile phase solutions (Iwata method; Clin Chem 35: 795-799, 1989). The Iwata method inadequately separated US-G and two hydroxy 17-ketosteroides, 11 beta-hydroxyetiocholanolone and 11 beta-hydroxyandrosterone, and it exhibits insufficient sensitivity for measuring traces of US-G in the urine of healthy subjects. We solved these problems by developing a new method which measures US-G in urine, as a free type by hydrolyzing the glucuronide type enzymatically, by normal phase HPLC on a Capcell-Pak Silica column with one kind of mobile phase solution. By this method, the levels of US excreted as a glucuronide in the urine of healthy subjects and of patients with Cushing's syndrome were determined as proportions of the levels of 11 beta-hydroxyandrosterone. The average daily urinary excretion of US was 971 micrograms (125-4,995 micrograms) in patients with Cushing's syndrome (n = 22: two males and 20 females aged 26 to 65 years), and 34 micrograms (0-141 micrograms) in healthy subjects (n = 63: 49 males, and 14 females aged 21 to 54 years), and the differences were clearly significant. However, there were no differences between the urinary US levels of patients with pituitary adenoma and patients with adrenal adenoma. Furthermore, no US was detected in the urine of patients with aldosteronism (two males and eight females aged 34 to 61 years).(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of acute hyperinsulinemia on plasma atrial and brain natriuretic peptide concentrations

Impaired renal sodium excretion and increased plasma atrial natriuretic peptide (ANP) levels have been reported in patients with hypertension associated with insulin resistance and hyperinsulinemia. To clarify the interrelationship between hyperinsulinemia and plasma natriuretic peptides, we investigated the effects of physiological and non-physiological hyperinsulinemia on the plasma ANP and brain natriuretic peptide (BNP) levels. Plasma immunoreactive insulin (IRI), ANP and BNP levels were determined by a euglycemic-hyperinsulinemic glucose clamp in 20 patients with non-insulin-dependent diabetes mellitus, by a glucose challenge test in 22 normal subjects and by an insulin challenge test in six normal subjects. Both in the glucose clamp and the glucose challenge test, plasma ANP showed a significant increase in association with increased plasma IRI and plasma volume. However, there was no significant correlation between the changes in plasma ANP levels and plasma IRI levels in view of the peak values and the area under the curve of their responses. In addition, the plasma ANP did not show any significant change despite the marked elevation of plasma IRI in the insulin challenge test. There was no significant change in plasma BNP under any of the hyperinsulinemic conditions. These findings provide in vivo evidence for the lack of a direct effect of acute hyperinsulinemia on natriuretic peptides, although the chronic effects of hyperinsulinemia remain to be elucidated.

Dopaminergic regulation of aldosterone secretion: its pathophysiologic significance in subsets of primary aldosteronism

Although aldosterone (Aldo.) secretion is regulated by various humoral factors, evidence has accumulated to support an involvement of dopaminergic system in its regulation. The pathophysiological significance of the dopaminergic system in primary aldosteronism (PA) however remains unknown. In the present study, we examined the effects of metoclopramide (MCP) on Aldo. secretion in normal subjects (n = 11) and patients with essential hypertension (EH, n = 8), aldosterone-producing adenoma (APA, n = 10), and idiopathic hyperaldosteronism (IHA, n = 6). Plasma Aldo., prolactin (PRL), renin, cortisol, serum sodium, and serum potassium levels were determined before and 30 min after i.v. bolus injection of 10 mg MCP at 9 a.m. Plasma Aldo. showed a significant increase after MCP in normal subjects, EH, and APA, but not in IHA. The incremental response of plasma Aldo. was largest in APA and smallest in IHA. The percentage increase in plasma Aldo. from the basal level was significantly attenuated in IHA, while no significant difference was seen among other groups. Although plasma PRL showed a significant increase in response to MCP, no difference of the change was seen among the groups. There was no significant change in plasma cortisol, renin, serum sodium, and serum potassium levels in response to MCP. In addition, the response of Aldo. to MCP was normalized in APA after unilateral adrenalectomy, while that of PRL did not change. These results indicate that the adrenal dopaminergic activity is enhanced in APA and attenuated in IHA and suggest an involvement of the dopaminergic system in the pathogenesis of IHA.(ABSTRACT TRUNCATED AT 250 WORDS)

Inhibin alpha, beta A subunit and activin type II receptor mRNAs are expressed in human brain tumors

Inhibin and activin were initially isolated as regulators of pituitary or gonadal hormone and are now known to be growth factors belonging to the TGF-beta family with diverse influences on the differentiation and proliferation of various tissues. To investigate the role of inhibin and activin in human brain tumors, the expression of inhibin alpha, and beta A mRNA as well as activin type II receptor (ACTR II) mRNA were studied in various human brain tumors. The tumors were divided into the following 4 groups: 3 Rathke's cleft cysts and 2 craniopharyngiomas (group 1), 8 meningiomas (group 2), 8 malignant gliomas (group 3), and various other tumors including 1 each of germinoma, astrocytoma, hemangioblastoma, and osteochondroma as well as 2 malignant lymphomas and 2 metastatic squamous cell carcinomas (group 4). Immediately after resection, tumor tissues were homogenized in guanidine thyiocyanate to extract total RNA. PCR was then performed with reverse-transcribed cDNA and the respective amplification primers. DNA bands were obtained by agarose gel electrophoresis. Messenger RNA for the inhibin beta A subunit was demonstrated in all of the tissues studied. In contrast, inhibin alpha subunit mRNA was expressed in 60%, 50%, 75%, and 75% of the tumors in groups 1, 2, 3 and 4, respectively, whereas ACTR II mRNA was demonstrated in 20%, 37.5%, 62.5% and 50% of the tumors in each group. Coexpression of mRNAs for the inhibin alpha, and beta A subunits and ACTR II occurred in some brain tumors. The levels of inhibin alpha and ACTR II mRNA tended to be higher in the tumors with a higher grade of malignancy.(ABSTRACT TRUNCATED AT 250 WORDS)

Leuprolide acetate prevents toxic effects of cisplatin on the kidneys and gastrointestinal tract

We examined the protective effects of medical castration by means of gonadotropin-releasing hormone analogue (GnRHA) on the toxic effects of cisplatin in rats. Twelve days after a s.c. injection of a slowly-releasable form of leuprolide acetate (GnRHASR), rats were injected i.p. with cisplatin daily (3 mg/kg body weight (BW) for males and 4 mg/kg BW for females) for four days and sacrificed 24 h after the last injection. The doses caused acute tubular necrosis and gastrointestinal (GI) symptoms, i.e., diarrhea and fluid retention and bleeding in GI tract. GnRHASR pretreatment reduced serum urea nitrogen (SUN) and serum creatinine (SCre) increase and the incidence of GI symptoms. Histological analysis showed that rats pretreated with GnRHASR had noticeably less kidney damage. GnRHA thus demonstrated its ability to protect the kidneys and GI tract against cisplatin toxicity in both male and female rats. This finding suggests a potential clinical application of GnRHA in antineoplastic chemotherapy.

Modulation of vascular natriuretic peptide receptor gene expression in hypertensive and obese hyperglycemic rats

Receptors for natriuretic peptide (NP) consist of three subtypes: NP-A, NP-B, and NP-C. Recent studies in cultured aortic cells have suggested a phenotype-related switching of the vascular NP receptor from NP-A to NP-B. To ascertain the biological significance of the phenomenon in vivo, we developed a sensitive and reproducible ribonuclease protection assay and determined each receptor messenger RNA (mRNA) level in the vascular vessels of stroke-prone spontaneously hypertensive rats, deoxycorticosterone acetate-salt hypertensive rats, and genetically hyperglycemic. Wistar fatty rats and in cultured aortic smooth muscle cells. The aortic NP-A receptor mRNA level was significantly up-regulated in both types of hypertensive rats, whereas the NP-B receptor mRNA level did not show any significant change. Both NP-A and NP-B receptor mRNA levels were significantly up-regulated in Wistar fatty rats compared with the control values. There was no significant up-regulation of NP-A receptor mRNA in the inferior vena cava of the stroke-prone spontaneously hypertensive rats. Although the NP-A receptor was always the predominant subtype in rat aortic tissue, NP-B receptor was the predominant subtype in aortic smooth muscle cells in culture. These findings suggest that up-regulation of the NP-A receptor, but not the subtype switching, is the major modulation of receptor gene expression in both hypertensive and diabetic rats.

Pathophysiological significance of plasma total renin and prorenin in patients with diabetes mellitus

To seek the pathophysiologic significance of measuring the concentration of total renin instead of prorenin, we determined the plasma total renin concentration by immunoradiometric assay and correlated the results with various clinical features and laboratory parameters of diabetic complication in 108 patients with diabetes mellitus. The plasma prorenin concentration was estimated as the difference between the total and active renin concentrations. The plasma total renin and prorenin concentrations were high in patients with diabetes mellitus, in contrast to the active renin concentration which was slightly decreased. In addition, the plasma total renin and prorenin concentrations were higher in patients with diabetic complications than in patients without any complication. Multiple regression analysis showed that the presence of orthostatic hypotension, diabetic retinopathy, and proteinuria is significantly associated with the increased plasma total renin and prorenin concentrations. In addition, there was a significant positive correlation between the total renin and prorenin concentrations. These results suggest that both the plasma total renin concentration and the prorenin concentration are closely related to diabetic complications. Determination of the plasma total renin concentration by immunoradiometric assay as a substitute for prorenin could be a powerful tool in elucidating the mechanism for the increased plasma prorenin in diabetes mellitus.

Intracerebroventricular administration of corticotropin-releasing factor antagonist attenuates c-fos mRNA expression in the paraventricular nucleus after stress

Corticotropin-releasing factor (CRF) plays a role in coordinating endocrine, physiological and behavioral responses to stressful stimuli. We have previously reported that centrally administered CRF rapidly induces c-fos mRNA expression in most areas that express c-fos following stress: the limbic structures including the hippocampus, amygdala, septal nucleus and hypothalamic nuclei such as the paraventricular nucleus (PVN), and brainstem nuclei such as Barrington's nucleus and locus ceruleus (LC). These results suggest several candidate structures through which CRF could exert its effects on the central nervous system. The aim of the present study was to explore the role of endogenous CRF in activating these brain regions after stress using a specific CRF receptor antagonist, alpha-helical CRF(9-41). One hundred micrograms of alpha-helical CRF or vehicle alone was injected into the right lateral ventricle of rats. Thirty minutes later, they were exposed to restraint stress for 30 min, and the rat brain was then perfused transcardially with 4% paraformaldehyde. Another control group of rats was sacrificed 60 min after intracerebroventricular (ICV) injection of vehicle without restraint. In situ hybridization was performed by hybridizing sections with 35S-labeled c-fos cRNA probes. ICV injection of vehicle alone induced a weak c-fos mRNA expression in the lateral septal nucleus (LSV) and PVN in the rats without restraint, probably due to the mild stress of ICV injection. Restraint stress produced strong c-fos mRNA induction in the PVN, LSV, LC and Barrington's nucleus. However, ICV injection of 100 micrograms alpha-helical CRF significantly decreased c-fos mRNA expression in the PVN without affecting c-fos mRNA induction in the LSV, LC, or Barrington's nucleus.(ABSTRACT TRUNCATED AT 250 WORDS)

Appropriate intravenous doses of L-thyroxine and magnesium in a thyroidectomized patient with thyroid and parathyroid carcinomas receiving total parenteral nutrition during acute necrotizing pancreatitis

A totally thyroidectomized patient with thyroid and parathyroid carcinomas, which had developed after neck irradiation in childhood, became hypercalcemic due to pulmonary metastases. The hypercalcemia was ameliorated by intermittent iv administration of bisphosphonate for 3.5 years, but this gradually became refractory to the bisphosphonate treatment. After right thoracotomy for resection of pulmonary metastases, acute necrotizing pancreatitis developed. The patient was therefore placed on total parenteral nutrition supplemented with T4 and a restricted dose of magnesium. Thyroxine(T4) (30 micrograms/day, iv) was not sufficient to maintain euthyroidism, but a higher dose (60 micrograms/day) elicited mild hyperthyroidism to the same extent as that elicited by an oral dose of 100 micrograms/day. The present case showed that the appropriate iv dose of T4 in this thyroidectomized patient with acute pancreatitis was about 60% of the oral dose. Furthermore, bisphosphonates (pamidronate and alendronate) and magnesium depletion were very effective in controlling the hypercalcemia.

Inhibition of growth hormone-releasing factor production in mouse placenta by cytokines using gp130 as a signal transducer

The aim of this study was to investigate whether mouse placenta produces mature mouse GHRF (mGHRF) and whether cytokines regulate placental mGHRF production. Using Sephadex G-50 gel filtration chromatography and reverse phase HPLC, we identified immunoreactive mGHRF in acid-ethanol extract of placental tissues, which had chromatographic characteristics identical to those of hypothalamic mature mGHRF peptide. The major peak of immunoreactive GHRF in the medium from cultured placental cells was resolved by HPLC at a fraction identical to hypothalamic mature mGHRF. Interleukin-6 (IL-6), IL-11, leukemia inhibitory factor (LIF), and oncostatin-M, which all use gp130 as a signal transducer, significantly inhibited mGHRF secretion by cultured placental cells. However, IL-1 alpha and tumor necrosis factor-alpha had no effect on mGHRF secretion. Antibodies to IL-6 or IL-6 receptor completely blocked the inhibitory effect of IL-6 on mGHRF secretion. Anti-LIF, and oncostatin-M inhibited the expression of mGHRF messenger RNA. These results suggest that mouse placenta produces and releases the mature mGHRF, which is indistinguishable by chromatographic criteria from that produced by the hypothalamus, and that signals through gp130 lead to the inhibition of mGHRF production and release in the mouse placenta.

Effects of transforming growth factor alpha (TGF-alpha) on DNA synthesis and thyrotropin-induced iodine metabolism in cultured porcine thyroid cells

Transforming growth factor alpha (TGF-alpha) is a potent mitogen that is similar structurally to epidermal growth factor (EGF). As EGF is a potent growth stimulator and an inhibitor of iodine metabolism in cultured thyroid cells of several species, we studied whether TGF-alpha has similar effects using porcine thyroid cells in culture. Recombinant human TGF-alpha dose-dependently stimulated DNA synthesis of thyroid cells, with maximal stimulation (eight- to ninefold above basal) occurring at 2 nmol/l. The potency was approximately 50% that of mouse EGF and correlated with the ability to compete with EGF for receptor binding, suggesting that the action of TGF-alpha is mediated by interaction with EGF receptors. When thyroid cells were cultured for 3 days with thyrotropin (TSH) in the presence of TGF-alpha, TSH-induced iodide uptake was inhibited in a dose-dependent manner. The potency of TGF-alpha again was approximately 50% that of EGF. Transforming growth factor alpha did not inhibit TSH-stimulated cAMP production. Moreover, iodide uptake stimulated by either forskolin or 8-bromo-cAMP also was inhibited by TGF-alpha. Thus, we conclude that TGF-alpha inhibits TSH-induced iodine metabolism largely by acting at the steps distal to cAMP production. Northern blot analysis revealed expression of TGF-alpha mRNA in porcine thyroid cells. These observations suggest that TGF-alpha acts as an autocrine modulator of growth and differentiated functions in porcine thyroid cells.