Plasma galanin, vasopressin, and oxytocin in patients with Addison's disease

Galanin is colocalized with adrenocorticotrophin (ACTH) in the human pituitary and with corticotrophin releasing hormone, arginine, vasopressin, and oxytocin in the hypothalamus. Galanin, vasopressin, and oxytocin influence the secretion of pituitary ACTH. The aim of this study was to investigate if the endogenous stimulation of ACTH release in Addison's disease was reflected in plasma galanin, vasopressin, and oxytocin. ACTH, galanin, vasopressin, and oxytocin were measured in plasma from 14 patients with Addison's disease, one patient with Nelson's syndrome, and 14 healthy controls. Eight patients had elevated plasma ACTH whereas six patients and all controls had ACTH levels within the reference-range. There was no difference in galanin or vasopressin between patients and controls or between samples with low or high ACTH concentrations. In contrast, oxytocin was higher in patients with elevated plasma ACTH compared to patients and controls with normal or low ACTH. No relation was found between galanin or oxytocin and age or sex. A tendency towards lower vasopressin with increasing age was found among the men (p=0.057). The highest ACTH and galanin levels were found in the patient with Nelson's syndrome. In conclusion, increased plasma ACTH was not reflected in elevated plasma galanin or vasopressin. In contrast, elevated ACTH levels were accompanied by higher oxytocin levels.

Effects of arginine-vasopressin and parathyroid hormone-related protein (1-34) on cell proliferation and production of YKL-40 in cultured chondrocytes from patients with rheumatoid arthritis and osteoarthritis

OBJECTIVE

Both arg-vasopressin (AVP) and parathyroid hormone-related protein (PTHrP) may act as proinflammatory hormones. In addition, they have been suggested to be involved in the pathophysiology of rheumatoid arthritis (RA). We therefore investigated the effects of AVP and PTHrP (1-34) on cell proliferation and secretion of the glycoprotein YKL-40 in human chondrocytes derived from healthy subjects as well as from patients with RA or osteoarthritis (OA).

METHOD

Primary cultures of human chondrocytes were incubated with AVP (1-100 pmol/l) or PTHrP (1-34) (0.1-100 nmol/l). Cell proliferation was measured as [3H]thymidine incorporation. Intracellular cAMP and YKL-40 in cell medium were determined by commercially available kits.

RESULTS

AVP and PTHrP (1-34) increased proliferation in chondrocytes derived from healthy donors as well as from RA and OA patients. PTHrP (1-34), but not AVP, increased intracellular levels of cAMP. PTHrP (1-34) did not change the amount of YKL-40 in chondrocytes from healthy subjects or patients with OA. AVP tended to decrease the secretion of YKL-40 from healthy chondrocytes. Both PTHrP (1-34) and AVP increased YKL-40 secretion from RA chondrocytes. In contrast, AVP decreased the secretion of YKL-40 in chondrocytes from patients with OA.

CONCLUSION

AVP and PTHrP (1-34) stimulated proliferation in human chondrocytes derived from healthy subjects as well as from patients with RA or OA. However, the effects of AVP and PTHrP (1-34) on YKL-40 secretion varied depending on the origin of the chondrocytes.

The effects of arg-vasopressin on osteoblast-like cells in endothelial nitric oxide synthase-knockout mice and their wild type counterparts

In the present study, we investigated whether nitric oxide (NO) could be involved in the effects of arg-vasopressin (AVP) on osteoblast-like cells. Cells derived from endothelial nitric oxide synthase (eNOS)-knockout mice and their wild type (WT) counterparts, and an osteosarcoma cell line (SaOS-2) were used. AVP (10-100 pmol/l) increased proliferation of osteoblast-like cells from WT mice. The effect was abolished by an AVP V1-receptor antagonist. AVP increased proliferation of cells from eNOSKO mice only when a NO donor, SNAP, was added. A nitric oxide synthase-inhibitor, L-NAME, antagonized the increase in cell proliferation in response to AVP in SaOS-2 cells. In conclusion, this study indicates that NO is involved in the effects of AVP on cell proliferation in osteoblast-like cells.

Galanin in human plasma

The neuropeptide galanin has important effects on hormone secretion from the hypothalamus and pituitary, and it may also be involved in central biological processes such as pain, memory, and food intake. Yet, there is limited knowledge about how these processes are reflected by circulating galanin. To study the levels and molecular forms of galanin in the human circulation, plasma was analysed from 26 healthy subjects, 14 women and 12 men, using two extraction methods and a specific radioimmunoassay for human galanin. Galanin-LI levels in unextracted plasma were higher (141-191 pmol/L) than after immunoextraction (3.4-30.7 pmol/L) and Sep Pak extraction (2.2-12.6 pmol/L). Galanin immunoreactivity after Sep Pak and immunoextraction correlated (r = 0.74, p<0.001). Galanin-LI levels were significantly higher in the men than in the women (p = 0.01) after Sep Pak extraction. A small increase in galanin-LI was seen with age in the women (r = 0.54, p < 0.05). The proportion of Sep Pak extracted galanin-LI increased with age in the women (r = 0.73, p < 0.05)) but not in the men.

Heterogeneous forms of immunoreactive galanin in human plasma; higher levels in men than in women

Galanin, a neuropeptide, has important effects on hormone secretion from the hypothalamus and pituitary, and may also be involved in important biological processes such as pain, memory, and food intake. Yet, there is limited knowledge about how these processes are reflected by circulating galanin. To study the levels and molecular forms of galanin in the human circulation, plasma was analysed from 27 healthy subjects, 14 women and 13 men, using two extraction methods and a specific radioimmunoassay for human galanin. After extraction on Sep Pak C-18 columns, plasma galanin-like immunoreactivity (galanin-LI) in the healthy men was 6.3 +/- 2.5 pmol/l (mean +/- SD, n = 12), which was higher than in the women, 4.1 +/- 1.5 pmol/l (n = 14, p = 0.010). A small increase in galanin-LI was seen with age in the women (r = 0.54, p < 0.05) but there was no significant difference between pre- and postmenopausal women. Galanin immunoreactivity after Sep Pak and immunoextraction correlated (r = 0.74, p < 0.001) the levels being higher after immunoextraction (p < 0.001). Gel chromatography disclosed heterogeneity of circulating galanin-LI with the majority eluting as homologs with a molecular weight higher than synthetic human galanin. Homologs smaller than galanin were also found. Sep Pak C-18 extraction eliminated the majority of the higher molecular forms. In conclusion, circulating galanin-LI was found to be higher in men and to be present mainly as molecular forms larger than synthetic galanin.

Inhibited anabolic effect of insulin-like growth factor-I on stromal bone marrow cells in endothelial nitric oxide synthase-knockout mice

AIMS

Insulin-like growth factor-I (IGF-I), parathyroid hormone (PTH) and PTH-related protein (PTHrP) are hormones that have anabolic effects on bone formation. The aim of this study was to investigate whether production of nitric oxide (NO) is involved in the effect of IGF-I and PTH/PTHrP on osteoblast-like cells.

METHODS

Bone marrow stromal cells from adult endothelial nitric oxide synthase (eNOS)-knockout (eNOSKO) mice and wild type (WT) counterparts were cultivated with osteogenic substances. The cells showed an osteoblastic phenotype measured as osteocalcin production and alkaline phosphatase activity. DNA synthesis was measured as [3H] thymidine incorporation in the bone marrow cells and in a human osteosarcoma cell-line (SaOS-2).

RESULTS

The stimulatory effect of IGF-I on thymidine incorporation seen in WT animals was absent in eNOSKO mice. Addition of a NO donor to eNOSKO cells recovered the effect of IGF-I on thymidine incorporation. PTH/PTHrP stimulated cell proliferation in both WT and eNOSKO mice. In SaOS-2 cells, incubation with IGF-I together with a NOS inhibitor resulted in an inhibition of the anabolic effect of IGF-I on cell proliferation.

CONCLUSIONS

The stimulatory effect of IGF-I on WT cell proliferation was abolished in eNOSKO cells, recovered by an NO donor and inhibited in osteosarcoma cells by a NOS inhibitor. The results indicate that the effect of IGF-I is dependent on NO production. The impaired IGF-I response may contribute to the bone defect formation seen in eNOSKO animals.

Weak evidence of thyrotropin receptors in primary cultures of human osteoblast-like cells

Extra-thyroidal thyrotropin (TSH) receptors (TSHRs) have been demonstrated in several tissues and cells, including human and rat osteosarcoma cell lines. We have explored whether human TSHR (hTSHRs) also are present in primary cultures of human osteoblast-like (hOB) cells. [(125) I]TSH binding was limited in hOB cells, but somewhat higher in UMR 106-01 cells and considerably higher in hTSHR-transfected CHO cells. In hOB cells, the basal intracellular cAMP levels increased 282% after stimulation with 10 U/L TSH. In the hTSHR-transfected CHO cells, the cAMP increase was 3030% in response to 10 U/L TSH and 1240% after 1 U/L TSH. Free cytoplasmic calcium did not change in response to TSH in hOB cells. HTSHR mRNA was detected in hOB cells from 3/4 bone by reverse transcriptase polymerase chain reaction RT-PCR and nucleotide sequencing HTSHR mRNA, but could not be demonstrated with the RNase protection technique in hOB cells from 5 different donors. In conclusion, even after the use of several methods, we have found only weak evidence for expression and presence of functionally active hTSHR in hOB cells. Given the low level of expression, specific binding and cAMP signaling, we suggest that it is unlikely that circulating TSH plays a physiological role for bone metabolism mediated through osteoblasts.

Extracellular calcium increases free cytoplasmic calcium and DNA synthesis in human osteoblasts

A high concentration of extracellular calcium (8 mM) induced an increase in free cytoplasmic calcium, a lower cyclic AMP level and increased DNA synthesis in primary cultures of human osteoblast-like cells. Inhibition of protein kinase C with bisindolylmaleimide I inhibited the stimulatory effect of extracellular calcium on DNA synthesis in human osteoblast-like cells, whereas inhibition of protein kinase A with Rp-cAMPs had no effect on DNA synthesis. This indicates that protein kinase C, possibly via increased free cytoplasmic calcium, mediates the effect of extracellular calcium on DNA synthesis in osteoblast-like cells rather than a relative decrease in cyclic AMP and protein kinase A activity. Furthermore, a low concentration (0.5 mM) of extracellular calcium decreased DNA synthesis. In conclusion, these data suggest that a high extracellular calcium level may be a coupling factor that recruits osteoblasts in the bone remodeling process, and that a low level of extracellular calcium may also regulate osteoblast function.

ATP dependent Ca2+ transport across basal membrane of human syncytiotrophoblast in pregnancies complicated by intrauterine growth restriction or diabetes

Neonates born after pregnancies complicated by diabetes or intrauterine growth restriction (IUGR) have increased incidence of hypocalcaemia. Furthermore, IUGR is associated with reduced bone mineralization in infancy and osteoporosis in adult life. We tested the hypothesis that placental calcium transport is altered in these pregnancy complications. Transport of calcium into syncytiotrophoblast basal plasma membrane (BM) vesicles was studied by rapid filtration and protein expression of Ca(2+) ATPase by Western blot. In IUGR Ca(2+) ATPase activity was increased by 48 per cent (n=13; P< 0.05) whereas protein expression was 15 per cent lower (n=13; P< 0.05) than in controls (n=16). Basal membrane ATP dependent calcium transport was unaltered in gestational diabetes (GDM) but increased by 54 per cent in insulin dependent diabetes (IDDM) compared to controls (P< 0.05; n =14). Diabetes did not affect Ca(2+) ATPase expression in BM. We have previously shown that the mid-molecular fragment of parathyroid hormone related peptide (PTHrP midmolecule) stimulates BM Ca(2+) ATPase in vitro. PTHrP midmolecule concentrations in umbilical cord plasma were measured using radioimmunoassay. The concentrations in umbilical cord plasma were increased in IUGR, but unaltered in diabetes. In conclusion, placental calcium pump is activated in IUGR and IDDM, which may be secondary to increased foetal calcium demand. We speculate that PTHrP midmolecule may be one mechanism for activating BM Ca(2+) ATPase in IUGR.

Synovial fluid from loose hip arthroplasties inhibits human osteoblasts

Aseptic loosening of prosthetic components in patients who have undergone total hip arthroplasty is a major clinical problem. Earlier studies on this topic have focused mainly on different aspects of bone resorption. The current study investigated the influence of synovial fluid from patients who underwent revision surgery because of aseptic loosening and synovial fluid from patients with osteoarthritis on the proliferation of primary cultures of human osteoblasts. Incubation of cells with 10% synovial fluid from patients who had revision surgery significantly inhibited [3H]thymidine incorporation into deoxyribonucleic acid in human osteoblasts compared with control conditions, whereas 10% synovial fluid from patients with osteoarthritis had a significant stimulatory effect. These findings correlate well with clinical features seen in these diseases, such as increased net bone resorption around the prosthesis in patients with loosening, and increased periarticular bone formation in patients with osteoarthritis.

Interleukin-1beta upregulates PTHrP-mRNA expression and protein production and decreases TGF-beta in normal human osteoblast-like cells

Osteoblasts are regulated by complex interactions among systemic hormones, cytokines, and local growth factors. Bone resorption, at the level of the basic multicellular unit, is initiated by stimulation of osteoblast activity. The stimulatory effect of interleukin-1beta (IL-1beta) on bone resorption has not been fully clarified. We have therefore studied the influence of IL-1beta on the local production and secretion of parathyroid hormone-related protein (PTHrP) and transforming growth factor-beta (TGF-beta) from normal human osteoblast-like cells (hOB cells). Using a quantitative PCR-assay following reverse transcription of RNA, in situ hybridization, and a two-site immunofluorometric assay for PTHrP, we demonstrate that IL-1beta in a dose- and time-dependent manner increases PTHrP-mRNA expression and PTHrP-protein secretion. In addition, IL-1beta decreased the TGF-beta protein concentration in conditioned medium. Our results suggest that the actions of IL-1beta on bone may be mediated by novel mechanisms involving both local increase of PTHrP, a potent stimulator of bone resorption, and a decrease of TGF-beta, an important anabolic and coupling factor for bone turnover.

Calcitonin-suppressed expression of parathyroid hormone-related protein in breast cancer cells

Parathyroid hormone-related protein (PTHrP) is a key factor behind humoral hypercalcemia of malignancy (HHM). It is produced in most breast tumors and may be an important local mediator of skeletal metastases due to breast cancer. PTHrP may mediate local bone destruction in the absence of increased circulating PTHrP. Calcitonin (CT) is used for treatment of HHM, but there are data showing that CT can increase PTHrP expression and secretion in vitro. We have therefore studied the effect of CT on PTHrP gene expression and secretion in MCF-7 breast cancer cells. PTHrP mRNA decreased significantly after 4, 8, and 16 h incubation with 10 nM salmon calcitonin (sCT) when compared with the respective controls. PTHrP mRNA also decreased significantly and dose-dependently after incubation with sCT at 0.1 to 10 nM for 16 h. The PTHrP levels in the conditioned medium also decreased in a similar dose-dependent manner. The adenylate cyclase agonist forskolin lowered the PTHrP mRNA dose-dependently. In cells exposed to varying concentrations of sCT for 15 min, the cAMP levels increased dose-dependently. In conclusion, sCT can suppress PTHrP gene expression in MCF-7 breast cancer cells. The suppressive effect is probably exerted mainly via the cAMP-protein kinase A pathways.

Two human osteoblast-like osteosarcoma cell lines show distinct expression and differential regulation of parathyroid hormone-related protein

Parathyroid hormone (PTH)-related protein (PTHrP) acts as a local regulator of osteoblast function via mechanisms that involve PTH/PTHrP receptors linked to protein kinase A (PKA) and C (PKC). However, the regulation of PTHrP production and mRNA expression in human osteoblasts is poorly understood. Here we have characterized alternative PTHrP mRNA 3' splicing variants, encoding PTHrP isoforms of 139, 141, and 173 amino acids, and studied the regulation of PTHrP and its mRNAs by activated PKA and PKC in two human osteoblast-like cell lines (KPDXM and TPXM). Using exon-specific Northern analysis and reverse transcriptase-coupled polymerase chain reaction, we identified mRNAs encoding PTHrP(1-139) and PTHrP(1-141) in both cell lines. PTHrP(1-139) mRNAs predominated in TPXM cells and PTHrP(1-173) mRNAs were only detected in TPXM cells. Activation of PKA or PKC resulted in different effects on PTHrP and its mRNAs in the two cell lines. In TPXM cells, peptide-specific immunoassays detected high basal levels of PTHrP, increasing by 2-fold in cell extracts and 4-fold in culture media at 7 h and 24 h after exposure to forskolin, respectively, paralleling changes in PTHrP mRNA expression. Phorbol ester 12-O-tetradecanoyl-phorbol 13-acetate (TPA), a PKC activator, had no effect. In KPDXM cells, PTHrP was not detected in culture media under basal experimental conditions, and barely detectable amounts were present in cell extracts of TPA-treated cells, although the mRNA levels increased substantially in response to TPA. In the responsive cell lines, the effects on mRNA levels were dose dependent, and increased by 6.9- to 10.5-fold and 2.0- to 4.1-fold at 4 h in TPXM and KPDXM cells after exposure to 10 microM forskolin and 150 nM TPA, respectively. PTHrP mRNA levels then declined but were sustained above controls also at 12 h in both cell lines, albeit at considerably higher levels in TPXM cells. The different responsiveness to agents activating PKA- and PKC-dependent pathways may depend on the cellular state of differentiation, or alternatively, cancer cell line-specific defects. Our data demonstrating distinct differences in mRNA species and the amounts of PTHrP produced by the two cell lines as compared with roughly equivalent overall mRNA levels may suggest that post-transcriptional mechanisms play an important role in limiting the production of intracellular and secreted PTHrPs in human osteoblastic cells.

Parathyroid hormone-related protein in patients with primary breast cancer and eucalcemia

Parathyroid hormone-related protein (PTHrP) is a causative factor of humoral hypercalcemia in breast cancer and other malignancies. We studied circulating PTHrP levels with three different immunoassays directed against different parts of the PTHrP molecule in 48 patients with breast cancer and eucalcemia. The methods used were: (a) a RIA with antibodies directed toward the midregion (63-78); (b) an immunofluorometric assay with two antibodies against 1-34 and 38-67; and (c) an immunoradiometric assay with antibodies against 1-40 and 1-72. Although most patients had PTHrP levels indistinguishable from normal when measured by all three methods, four patients had increased serum levels in the IFMA. PTHrP was detected by immunohistochemistry in tumors from nearly all patients. One patient with elevated PTHrP in plasma measured by IFMA showed intense staining of tumor by immunohistochemistry; the tumor was histologically graded as III (severe) and was the largest of all tumors in this patient group. The IFMA can identify increased serum PTHrP in some patients with breast cancer who are not hypercalcemic. This assay may be especially useful in screening patients for this tumor during a relative early phase of the disease.

Parathyroid hormone-related protein (1-37) induces cAMP response in human osteoblast-like cells

During recent years parathyroid hormone-related protein (PTHrP) research has been focused on the physiological functions of different fragments of the PTHrP molecule. Here we demonstrate that PTHrP (1-37) induced cyclic adenosine monophosphate (cAMP) response in primary human osteoblast-like cells, which were well characterized by the presence of alkaline phosphatase activity and osteocalcin production after stimulation with 1,25-dihydroxyvitamin D3. However, there was no cAMP response to PTHrP (58-77). Furthermore, the response to PTHrP (1-37) was dose dependent, with a significant increase at 1 nM. The presence of PTHrP (1-37)-induced cAMP response in human osteoblast-like cells implies that aminoterminal PTHrP fragments may exert important functions in the bone.

Quantification of parathyroid hormone-related protein mRNA by competitive PCR and time-resolved lanthanide fluorometry

Using dissociation and enhancement time-resolved lanthanide fluorometry, we have developed a quantitative competitive (QC)-PCR for measuring parathyroid hormone-related protein (PTHrP) mRNA after reverse transcription. A cloned PTHrP cDNA target was also modified by deletion of 10 bp and insertion of 21 bp in the midregion of the fragment and cloned for use as a competitor (i.e., internal standard). Two primers spanning 362 bp of target and 373 bp of competitor were designed and one of the primers was biotinylated. Two oligonucleotide probes, one recognizing the target and the other hybridizing to the competitor, were labeled with Eu chelate. Two equal aliquots of PCR products were assayed with each probe separately in streptavidin-coated wells. After 35 PCR cycles, the competitor signal decreased exponentially (y = e(3.74 - 0.624x); r2 = 0.965) and the target signal increased exponentially (y = e(1.14 + 0.497x); r2 = 0.984) when 1000 copies/tube of the competitor and 0-100,000 copies/tube of the target DNA were added. Log-transformed data for the ratio of target to competitor signals (y) and the copies of the target DNA added (x) were used for plotting the linear calibration curve (y = 2.79 + 2.76x; r2 = 0.976). This QC-PCR enables analysis of multiple samples simultaneously and can be used to study PTHrP gene expression in malignancy and physiology.

Effect of acute endurance and strength exercise on circulating calcium-regulating hormones and bone markers in young healthy males

Physical activity plays a role in the maintenance of the skeleton but the mechanical, metabolic and hormonal mechanisms involved are largely unknown. The influence of acute endurance and strength exercise on circulating levels of calcitonin, parathyroid hormone (PTH), PTH-related peptide (PTHrP), osteocalcin, carboxyterminal cross-linked telopeptide of type I collagen (ICTP) and ionized calcium (Ca2+) was therefore evaluated. Eight healthy young males performed three exercise bouts on separate occasions: endurance exercise, i.e. cycling on a cycle ergometer for 45 min at 55% of Vo2max (E55%) and 15 min at 85% of Vo2max (E85%) and strength exercise at 85% of three repetitions maximum using a leg-press device (STR). Control experiments included the same subjects with the same time schedule but without exercise. Blood samples were taken before, immediately after exercise and during the recovery period. Hormones and bone markers were measured by use of various immunoassays. There was no obvious influence on calcitonin and PTHrP levels, whereas PTH was increased after strength exercise. ICTP and osteocalcin levels correlated positively at all times and showed regular variations. In comparison with the controls, ICTP levels showed a more pronounced decrease following physical activity whereas osteocalcin followed the same pattern as the controls except for after prolonged endurance exercise when a decrease was abolished. In conclusion, an increase in PTH after strength exercise and a pronounced decrease in ICTP after all exercise together with a relative increase in osteocalcin after prolonged endurance exercise might reflect some mechanisms involved in the positive effect of physical activity on bone mass.

Parathyroid hormone-related protein in neonatal and reproductive goats determined by a sensitive time-resolved immunofluorometric assay

OBJECTIVE

High concentrations of parathyroid hormone-related protein (PTHrP) have been found in goat milk but it is not known whether it can enter the circulation of the neonate. In this study we have developed a sensitive two-site lanthanide immunofluorometric assay (IFMA) using dissociation and enhancement time-resolved fluorometry to address this question.

METHOD

Affinity-purified anti-PTHrP 38-67 raised in rabbit was biotinylated and immobilized in streptavidin-coated microtitration wells as a 'capture' antibody. As a signal, affinity-purified anti-PTHrP 1-34, raised in sheep, was labeled with an europium chelate. A sensitivity of 0.3 pmol/l was achieved. PTHrP levels were determined in the plasma of eleven neonatal, seven parturient and six non-pregnant, non-lactating goats as well as in goat milk.

RESULTS

The circulating PTHrP levels (mean +/- S.D.) were significantly increased at day 1 (6.1 +/- 1.7 pmol/l: P < 0.01) and day 3 (3.5 +/- 0.6 pmol/l: P < 0.05) after birth in the male kids (n = 8) bottle-fed with milk from the dams, compared with before (2.2 +/- 0.7 pmol/l) and 30 min after (2.0 +/- 0.6 pmol/l) the first feeding and 14 days (2.4 +/- 0.8 pmol/l) later. In the female kids (n = 3) fed with formula there was no such increase and the concentrations remained between 1.6-1.9 pmol/l. In the parturient goats the mean +/- S.D. PTHrP levels before, during and after parturition were 2.9 +/- 1.7, 4.2 +/- 2.4 and 3.7 +/- 2.2 pmol/l respectively (n = 7) which demonstrated that plasma PTHrP was higher during and after parturition in comparison with before (P < 0.05). The levels in non-pregnant, non-lactating goats were 3.3 +/- 1.5 pmol/l (n = 6). PTHrP levels in goat milk were in the nanomolar range and were highest in the colostrum.

CONCLUSIONS

A significant increase of plasma PTHrP was observed in goat kids fed with milk from their dams and this increase was not found in kids fed with formula. Plasma PTHrP was also increased during parturition.

Two-site immunofluorometric assay of intact salmon calcitonin with improved sensitivity

We recently developed a two-site immunofluorometric assay (IFMA) of salmon calcitonin (SCT) by DELFIA (dissociation enhancement lanthanide fluoroimmunoassay) technique using the same polyclonal antibodies both for "catching" the antigen and for signaling. In the present study we used a monoclonal antibody to SCT 1-11 as the capture antibody. This antibody was biotinylated before use in streptavidin-coated microtitration plates. The polyclonal antibody labeled with Eu chelate was used as a signaling marker. This combination of antibodies resulted in an assay that was three to four times more sensitive than the previous IFMA, with a detection limit of 0.3 pmol/L serum. Intact SCT 1-32 was detected by the assay (recoveries 94-96%), but not the fragments SCT 1-11 and SCT 10-32 or human calcitonin. Dilutions of plasma samples containing SCT were parallel to the calibration curve of SCT 1-32. Pharmacokinetic studies of SCT, 100 IU administered intramuscularly to 10 men, indicated peak serum concentrations of 32-128 pmol/L within 10-20 min with apparent half-life of 56+/-18 min (mean+/-SD). This new assay will allow study of the pharmacokinetics of new calcitonin preparations that do not require injection.

Estimation of the C-cell numbers in rat thyroid glands using the optical fractionator

We estimated the total number of calcitonin-immunoreactive C-cells in rat thyroid gland using the optical fractionator, the unbiased stereological method for estimation of numbers. It was necessary first to use a fixative composed of formalin, acetic acid, and ethanol to distinctly visualize the C-cells. The 40-microm-thick sections had to adhere to chromalum-gelatin-coated Superfrost Plus glass slides, and the immunostaining technique had to stain the C-cells evenly throughout the whole sections. Because the C-cells were irregularly distributed in the thyroid tissues, their counting required screening of about 500 fields per lobe, but the number of C-cells counted need not be high, about 90 per lobe. We estimated that rats have 185,000 +/- 42,000 C-cells (mean +/- SD; n - 7). The C-cell population did not differ significantly between the two lobes of a given rat, but it varied markedly among rats. The biological differences among the animals contributed 83% to the observed variability, whereas the methodological uncertainty contributed 17%. The serum levels of calcitonin and calcium were not closely correlated to the C-cell numbers. Our results indicate that variability in C-cell experiments can be reduced most effectively by increasing the number of animals used. However, the similar C-cell frequency found in the two thyroid lobes of each rat allows the use of one uniformly sampled lobe for quantification and the other lobe for further analysis.

Circulating monomer-like calcitonin in osteoporotic patients

Physiological concentrations of monomeric calcitonin can inhibit osteoclastic bone resorption in vitro. We therefore investigated the circulating molecular forms, including monomer-like calcitonin, and their concentrations in 9 men and 9 women with established osteoporosis. Calcitonin was immunoextracted from serum by the use of rabbit calcitonin antibodies coupled to Sepharose 4B. The lyophilized extracts were incubated with 6 M urea overnight and gel chromatographed in a fast protein liquid chromatography (FPLC) system; calcitonin was measured by radioimmunoassay in the fractions. FPLC disclosed immunoreactive calcitonin of three different molecular sizes in the patients. The two largest forms were approximately 30 and 10 kDa and one eluted at the same position as monomeric calcitonin (3.4 kDa). After extraction and FPLC we found slightly higher calcitonin concentrations in osteoporotic women than previously reported levels in age-matched healthy women. Male patients had higher levels than female patients. None of the osteoporotic patients lacked monomer-like calcitonin. There was no significant correlation between the extracted total or monomer-like calcitonin and bone mineral density of the femoral neck. It is concluded that the circulating calcitonin in both male and female patients comprises three different molecular forms and that there is no deficiency of the monomer-like form. The calcitonin levels in the female patients were slightly higher than in a previous control group.

Midmolecular parathyroid hormone-related peptide in serum during pregnancy, lactation and in umbilical cord blood

Indications of an important physiological role of parathyroid hormone-related peptide (PTHrP) for fetal calcium homeostasis, maternal-fetal calcium transport and reproduction have accumulated over recent years. The PTHrP concentrations were measured by an earlier developed midregion radio-immunoassay in serum from lactating healthy females and umbilical cord blood and compared with levels in age-matched non-pregnant or lactating females. The PTHrP concentrations could be measured in all samples after silica cartridge C18 extraction of 10-12 ml of serum. The concentrations were significantly higher during lactation (mean +/- SD: 0.72 +/- 0.14 pmol/l, N = 22) and in umbilical cord blood (0.85 +/- 0.18 pmol/l, N = 12) compared with healthy age-matched women (0.48 +/- 0.09 pmol/l, N = 10, p < 0.001). The molecular forms of PTHrP were also studied in an age-matched control group, in pregnant women and in umbilical cord blood by gel chromatography in a fast protein liquid chromatography system of Sep-Pak-extracted pooled serum. In all three groups we found heterogeneity of the molecular forms with two predominant peaks. The smallest fragment had a molecular weight of 4-6 kD while the largest form appeared as a high-molecular-weight molecule. In conclusion, the concentrations of midmolecule PTHrP fragments in serum are elevated during lactation and in umbilical cord blood. Because the midregion of PTHrP has unique actions, our results indicate that PTHrP may play an important physiological role for the mother and for the maternal-fetal calcium transport.

Serum calcitonin forms and concentrations in young and elderly healthy females

To further investigate the role of calcitonin (CT) in normal physiology we studied circulating forms and the secretion after "calcium clamp" in young and elderly healthy females. Heterogeneity of CT in serum was disclosed after immunoextraction, fast protein liquid chromatography, and radioimmunoassay in young (27 +/- 3 years; mean +/- SD, n = 6) and elderly females (69 +/- 6 years, n = 11). Three distinct molecular forms appeared with approximate mol wt of 30, 10, and 3-4 kDa. All young women studied had considerable amounts of circulating monomer-like CT whereas several elderly had undetectable or low levels. The influence of age on basal and calcium stimulated, immunoextracted CT in serum was also studied in young (26 +/- 4 years; mean +/- SD, n = 13) and elderly (63 +/- 6 years; n = 12) healthy females. The calcium stimulation was carried out by means of the standardized calcium clamp method, where calcium was kept on a presettled level at 1.45 mmol/liter (+/- 2%) for 60 minutes. CT was immunoextracted from serum in all series of experiments with a polyclonal antiserum directed against the mid- and carboxyterminal region of the CT molecule, and the amount of extracted CT was determined by radioimmunoassay using another polyclonal antiserum against the carboxyterminal portion. After calcium infusion, the increase in CT was significantly higher in young women than in elderly (P < 0.05). At basal conditions, the CT levels were not significantly different but slightly higher in young than in elderly females. In conclusion, several elderly women lack monomer-like calcitonin in serum in contrast to young women.(ABSTRACT TRUNCATED AT 250 WORDS)

Pronounced elevation in circulating calcitonin in critical care patients is related to the severity of illness and survival

OBJECTIVE

To study circulating levels of calcitonin in critically ill patients in relation to the severity of illness and survival.

DESIGN

Cross-sectional and prospective.

SETTING

The ICU in Gävle hospital, a secondary non-teaching hospital.

PATIENTS

37 consecutive ICU patients.

MEASUREMENTS AND RESULTS

Serum calcium and immunoreactive calcitonin (iCT) were measured and the Apache II and the Multiple Organ Failure (MOF) scores were recorded during the first 24 h in the ICU. Patients were followed for hospital survival. Profound increase in circulating iCT was seen (mean 591, median 184, range 8-3445 pg/ml) in the studied sample and only 11% of the patients showed normal levels (< 40 pg/ml). iCT was higher in septic than nonseptic patients (p < 0.004) and was correlated to two indices of severity of illness (r = 0.50, p < 0.006 versus the Apache II score and p = 0.55, p < 0.003 versus the MOF score). Furthermore, iCT was correlated to the length of stay in the intensive care unit (r = 0.56, p < 0.001) and was elevated in the patients who did not survive when compared to survivors (p < 0.03). iCT was not significantly related to the degree of serum calcium (mean 2.22 +/- 0.15 SD mmol/l). Gel chromatography in a fast protein liquid chromatography (FPLC) system of serum from 4 patients with elevated iCT disclosed that a majority of the measured CT was not due to monomeric CT, but high molecular CT.

CONCLUSIONS

Pronounced elevations in circulating iCT were seen during the first 24 h critically ill patients. As the major part of the iCT consisted of high molecular weight CT this would not induce hypocalcemia. Rather, the elevated iCT would be regarded as a part of the metabolic responses to illness.

Sensitive time-resolved fluoroimmunoassay of salmon calcitonin

A two-site assay was developed by use of the "dissociation and enhancement lanthanide fluoroimmunoassay" (DELFIA) technique for determination of salmon calcitonin (SCT) in serum after administration to osteoporotic patients. Polyclonal antibodies were produced in rabbits immunized with SCT coupled to ovalbumin. After affinity purification, the antibodies were used both as immobilized capture antibodies and as Eu-chelate-labeled signal antibodies. A sensitive assay with a detection limit of 1.1 pmol/L was achieved, and no cross-reaction with human calcitonin was observed. The intra- and interassay CVs were < 12% (n = 10) and < 15% (n = 4), respectively. Analytical recovery of SCT added to serum was 91% +/- 3% (mean +/- SD, n = 4). SCT was measurable in all the samples from eight osteoporotic patients after subcutaneous SCT administration. We conclude that this new sensitive and specific two-site DELFIA can reliably measure SCT in serum.

Sensitive time-resolved fluoroimmunoassay of salmon calcitonin

A two-site assay was developed by use of the "dissociation and enhancement lanthanide fluoroimmunoassay" (DELFIA) technique for determination of salmon calcitonin (SCT) in serum after administration to osteoporotic patients. Polyclonal antibodies were produced in rabbits immunized with SCT coupled to ovalbumin. After affinity purification, the antibodies were used both as immobilized capture antibodies and as Eu-chelate-labeled signal antibodies. A sensitive assay with a detection limit of 1.1 pmol/L was achieved, and no cross-reaction with human calcitonin was observed. The intra- and interassay CVs were &lt; 12% (n = 10) and &lt; 15% (n = 4), respectively. Analytical recovery of SCT added to serum was 91% +/- 3% (mean +/- SD, n = 4). SCT was measurable in all the samples from eight osteoporotic patients after subcutaneous SCT administration. We conclude that this new sensitive and specific two-site DELFIA can reliably measure SCT in serum.

Polyamines regulate human medullary thyroid carcinoma TT-cell proliferation and secretion of calcitonin and calcitonin gene-related peptide

The significance of polyamines for the neoplastic proliferation and secretion of calcitonin (CT) and calcitonin-gene-related peptide (CGRP) by the human medullary thyroid carcinoma TT cell line was investigated. TT cells were cultured in vitro for 6 days with or without additions of pathway inhibitors of polyamine biosynthetic enzymes. Treatment of the cells with 1 mM of the specific L-ornithine decarboxylase (ODC) inhibitor DL-alpha-difluoromethylornithine (DFMO) resulted in a 97% decrease in ODC activity, lowered contents of putrescine (96%) and spermidine (85%) and cell proliferation rates (90%) along with a compensatory 15-fold increase in S-adenosyl-L-methionine decarboxylase (SAMDC) activity. DFMO treatment also led to a decrease in cellular content of CT (33%) and CGRP (26%), while the drug enhanced secretion of CT (31%) but depressed that of CGRP (26%), and elevated the ratio of CT to CGRP secreted into the medium by 74%. Ethylglyoxal bis(guanylhydrazone) (EGBG), a SAMDC inhibitor, at 100 microM evoked a similar reduction of cell proliferation and lowered the content of spermine by 81%. Furthermore, EGBG treatment caused a 34-fold increase in ODC activity and a subsequent 35-fold build-up of putrescine, but also seemed to stabilize SAMDC as evidenced by a highly enhanced SAMDC activity (approximately 200-fold) during enzyme assays in the absence of the inhibitor. EGBG exposure resulted in an increase in cellular CT content (110%) and secretion of the hormone (82%), while not affecting CGRP content or release.2+ EGBG effects were partially counteracted by DFMO.(ABSTRACT TRUNCATED AT 250 WORDS)

Calcium homeostasis in normal pregnancy and puerperium. A longitudinal study

Calcium homeostasis was longitudinally followed in serum and urine throughout normal pregnancy and the puerperium in 23 healthy women. From the 14th week of gestation, samples were obtained every fourth week until the 38th week. Post partum samples were obtained on the fifth day and after eight weeks. In the serum the total calcium decreased continuously during pregnancy. The ionized calcium and phosphate levels remained unchanged and within the reference interval for non-pregnant women. The alkaline phosphatase level progressively increased and high levels were found at term. The magnesium and hematocrit values remained below, whereas the calcitonin level remained just above the reference interval throughout pregnancy. The parathyroid hormone was low initially and increased towards term but within the reference interval. The urine excretion of calcium was constantly high, close to the upper reference limit, and renal function was slightly improved. At the last sampling eight weeks after delivery, all values were within normal limits for non-pregnant women. Calcium homeostasis is considerably changed during pregnancy and non-pregnant reference limits are not often valid.

Blood sampling procedures influence serum calcitonin concentrations in rats

The aim of this study was to determine whether serum calcitonin (S-CT) in rats is influenced by the method of taking blood samples. Sampling during halothane anaesthesia, after repeated administration of anaesthesia after a 14-day interval, and sampling without the use of anaesthetics (i.e. after the rats were made unconscious by stunning), resulted in different S-CT values (P < or = 0.001), whereas Ca2+ levels were not affected. In thyroidectomized rats, the S-CT values after stunning were not significantly different whereas those in sham-operated rats were different (P < or = 0.01). The possibility that anaesthesia may suppress stunning-induced changes in S-CT was explored in three other groups of rats subjected to halothane anaesthesia, stunning and stunning under halothane anaesthesia respectively. Although the S-CT level was highest after stunning and lowest in halothane-anaesthetized rats (P < or = 0.001), anaesthesia did not suppress the effect of stunning on S-CT. In conclusion the effect of sampling procedures must be considered in studies on the levels of S-CT in rats.

Parathyroid hormone-related protein is produced by cultured endothelial cells: a possible role in angiogenesis

Parathyroid hormone-related protein (PTHrP) is produced by various normal and neoplastic tissues. Even if the physiological function(s) of PTHrP is unclear, evidence suggests that the protein may participate in the local regulation of smooth muscle contractility. We show here that PTHrP is produced in endothelial cells cultured from human umbilical veins as demonstrated both at the mRNA and protein level. The expression of PTHrP can be upregulated by the phorbol ester 12-O-tetradecanoyl-phorbol-13-acetate, which is known to stimulate endothelial cell differentiation and angiogenesis in vitro. Unlike smooth muscle cells, the endothelial cells do not express the parathyroid hormone (PTH)/PTHrP receptor mRNA, nor could specific binding of the protein be detected. We therefore suggest that PTHrP produced by endothelial cells acts on smooth muscle cells and may be of importance for the growth and development of new vasculature.

Plasma calcitonin, IGF-I levels and vertebral bone mineral density in hyperprolactinemic women during bromocriptine treatment

Hyperprolactinemia is associated with decreased bone mineral density, which may be caused by the hypogonadism and hypoestrogenicity noticed in patients with hyperprolactinemia. Since calcitonin inhibits the bone resorption, and insulin-like growth factor I (IGF-I) has important anabolic effects on the skeleton, lack of one or both peptides may contribute to the development of osteopenia. We therefore measured the plasma calcitonin and IGF-I levels in nine women with hyperprolactinemia caused by a prolactin-producing pituitary tumor. The calcium-stimulated C-cell reactivity was studied by measuring calcitonin in plasma during a calcium clamp before and after normalization of serum prolactin during treatment with bromocriptine. Basal CT levels were measurable but lower than in healthy controls. Basal IGF-I levels and calcium-stimulated plasma calcitonin were normal in the hyperprolactinemic state and similar to the calcitonin and IGF-I levels during bromocriptine treatment. The serum prolactin levels decreased (p < 0.001) and the serum estradiol levels increased (p < 0.001). The bone mineral density of the lumbar spine increased significantly during treatment. Thus, basal plasma CT levels are slightly reduced in hyperprolactinemic women. However, the reversible osteopenia in hyperprolactinemic women is less likely to be caused by inhibited IGF-I secretion or by deficient CT levels since the CT response to calcium is normal. In addition, bromocriptine treatment with normalization of prolactin levels is beneficial for the bone mineral content in this condition.

Influence of smoking and snuff use on electrolytes, adrenal and calcium regulating hormones

Little is known about the effects of snuff use on health. We have investigated electrolyte levels, adrenocortical and calcium regulating hormones in three groups of healthy young men, including 18 non-tobacco users, 21 snuff users and 19 smokers with similar age and body mass index. Smoking and snuff use was positively associated with alcohol and coffee consumption and inversely related to physical activity. Compared to non-tobacco users, smokers had significantly increased levels of serum sodium and magnesium, plasma calcitonin, urinary cortisol and potassium levels and decreased serum sex hormone-binding globulin as well as serum and urinary creatinine values. However, only decreased sexual hormone-binding globulin and urinary creatinine and increased serum phosphate and urinary potassium levels were seen in snuff users. Among tobacco users we noted that smokers differed from snuff users in that they had higher serum sodium (1.4 mmol/l, p < 0.01), plasma calcitonin (3.3 pmol/l, p < 0.05) and urinary cortisol (41 nmol/24 h, p < 0.05) but lower serum creatinine (5.8 mumol/l, p < 0.01). We conclude that chronic snuff use appears to have less influence on hormone and electrolyte balance than does smoking, and that some of the abnormalities seen in smokers do not seem to be mediated by nicotine.

Parathyroid hormone-related peptide, measured by a midmolecule radioimmunoassay, in various hypercalcaemic and normocalcaemic conditions

The diagnosis of humoral hypercalcaemia of malignancy often presents considerable clinical problems. We have studied parathyroid hormone-related peptide (PTHrP) in serum from patients with humoral hypercalcaemia of malignancy (N = 22), hypercalcaemia of malignancy with skeletal metastases (17), histologically confirmed primary hyperparathyroidism (21) and hypercalcaemic patients with various benign diseases (9). PTHrP measurements were also made in normocalcaemic patients with various malignancies (23), endocrine diseases (13), sarcoidosis (22) and chronic renal failure (17). PTHrP was measured by a novel radioimmunoassay using rabbit antibodies directed towards the midregion of the molecule. Immuno- or silica cartridge extraction of serum before radioimmunoassay enabled us to measure PTHrP in all samples, which may add further information about circulating forms of PTHrP. PTHrP was clearly elevated in patients with humoral hypercalcaemia of malignancy (5.0 +/- 4.7 pmol/l) (mean +/- SD, N = 12) and when the kidney function was impaired (4.0 +/- 0.9 pmol/l) (N = 15) (silica cartridge extraction), whether the subject was hypercalcaemic or not. Some patients with endocrine diseases, including two with primary hyperparathyroidism, had slightly elevated serum PTHrP concentrations, while they were normal in sarcoidosis. In healthy subjects the levels were 1.1 +/- 0.5 pmol/l (N = 15) after immunoextraction and 0.8 +/- 0.2 pmol/l (N = 33) after silica cartridge extraction.

Calcium homeostasis in pregnancy during long-term heparin treatment

OBJECTIVE

To investigate the effect of subcutaneous heparin treatment on calcium homeostasis in pregnancy.

DESIGN

A longitudinal case-control observational study.

SETTING

Department of Obstetrics and Gynaecology, Karolinska Hospital, Stockholm, Sweden.

SUBJECTS

36 pregnant women with previously verified thromboembolic complications and 23 healthy pregnant control women similar in age, parity, weight, and smoking habit.

INTERVENTIONS

Thromboprophylaxis during pregnancy and 6 weeks post partum was given with subcutaneous heparin twice daily to the 36 women with a history of thromboembolic complications, 16 received an average dose of 24,500 IU/day and 20 a mean dose of 17,300 IU/day. Venous blood and urine samples were obtained every 4 weeks.

MAIN OUTCOME MEASURES

Serum concentrations of total calcium, ionized calcium, calcitonin and urinary calcium.

RESULTS

Women on high-dose heparin treatment showed significantly higher concentrations of total and ionized calcium and of calcitonin in serum and significantly lower concentrations of calcium in urine than did 23 normal pregnant controls. The differences were most pronounced in the third trimester. The results obtained in the low-dose heparin group were between those in the high-dose and the control groups. At 8 weeks postpartum there were no significant differences between the heparin-treated women and the controls. No significant differences were found during pregnancy in haematocrit, liver or renal function, serum levels of albumin, phosphate, magnesium, alkaline phosphatase, parathyroid hormone or urinary cyclic AMP.

CONCLUSIONS

Heparin treatment during pregnancy results in changes in calcium homeostasis and a dose-dependent response is suggested.

Parathyroid hormone-related peptide in human milk measured by a mid-molecule radioimmunoassay

Several peptide hormones and growth factors have been found in human milk, and we present here the results of measurements of parathyroid hormone-related peptide (PTHrP). A radioimmunoassay (RIA) using a polyclonal antiserum against the mid-region of the molecule has been developed. In milk collected during the first 6 days after parturition, the PTHrP concentrations showed large interindividual variations ranging from 0.3 to 13.7 nmol-Eq/L (0.5 to 24.4 ng-Eq/mL) (n = 67) and increased between days 3 and five postpartum. PTHrP also increased during the first 4 collecting days when measured in milk from the same mother during a prolonged period. On fast-protein liquid chromatography (FPLC), the bulk of PTHrP eluted with a molecular weight of approximately 10 to 12 kd after treatment with urea. After mid-molecule immunoaffinity extraction of PTHrP from milk, higher levels were obtained by the mid-molecule RIA than by an aminoterminal assay, indicating that all fragments did not contain the aminoterminal. Parts of immunoextracted milk PTHrP stimulated cyclic adenosine monophosphate (cAMP) production in rat osteosarcoma cell line, UMR-106. In conclusion, we have found PTHrP-like immunoreactivity in human milk using a mid-region RIA. Parts of the immunoextracts also contained the aminoterminal and possessed PTH-like bioactivity. Whether PTHrP in human milk plays a physiological role in the maternal breast or in the newborn gastrointestinal tract is unknown, but the present observations demonstrate that a portion of the PTHrP is at least potentially biologically active.

A rapid extraction method for serum calcitonin

A rapid, simple and reliable extraction method for calcitonin from serum has been developed. 2 volumes of acidic ethanol and 1 volume of serum were mixed, centrifuged, and the supernatant was evaporated to dryness. The extracts were reconstituted in assay buffer before radioimmunoassay was performed. Basal concentrations of calcitonin after extraction were 5.4 +/- 3.0 pg-equivalents/ml (mean +/- SD), females, n = 48 and 8.8 +/- 5.5 pg-equivalents/ml, males, n = 42. Calcitonin was detectable in serum from all males and from 90% of the females. The concentrations in males were significantly higher (P less than 0.001). There was a more pronounced calcitonin response in males (n = 12) than in females (n = 12) to a calcium clamp (P less than 0.01). Gel chromatography of serum from patients with medullary thyroid carcinoma on a Sephadex G-75 column and a TSK G 2000 SW column in a fast protein liquid chromatography system, disclosed that the ethanol extraction excluded the high mol mass forms of calcitonin. We propose the acidic ethanol extraction as a convenient method for routine measurements of calcitonin.

Salmon calcitonin treatment by nasal spray in primary hyperparathyroidism

The hypocalcemic and hypophosphatemic effect of salmon calcitonin (sCT) given by intranasal (i.n.) spray to 12 patients with histological confirmed primary hyperparathyroidism (1 degree HPT) was studied. The concentration of ionized calcium in whole blood (B-Ca++), serum phosphate (S-P), magnesium (S-Mg), plasma sCT (Pl-sCT), and endogenous CT (hCT) was followed during five 24-hour periods with at least three days between. After period I (control day), 100 IU sCT was given intramuscularly (i.m.) in period II. In periods III-V, either 110, 200, or 400 IU of sCT were given intranasally (i.n.) in randomized order. Although B-Ca++ decreased from the baseline value with all four sCT treatments and at 4.5 hour on the control day (p less than 0.05-0.001), the i.n. sCT treatments had no significant hypocalcemic effect, as the change of the area under the B-Ca++ curve (delta AUC B-Ca++) for the three i.n. treatments was not significantly different from the control period (p less than 0.001, ANOVA). Only the i.m. injection of calcitonin had a calcium-lowering effect (p less than 0.001, ANOVA). Three subjects were considered nonresponders with a decrease in B-Ca++ less than 0.06 mmol/L. S-P decreased within three hours after 200 IU sCT i.n. and 100 IU i.m., but the S-Mg levels showed no consistent changes. The area under the curve for the Pl-sCT levels did not correlate with delta AUC B-Ca++ except for i.m. given sCT.(ABSTRACT TRUNCATED AT 250 WORDS)

Plasma calcitonin levels in patients with cystic fibrosis

Plasma levels of calcitonin were investigated in patients with cystic fibrosis and compared with age- and sex-matched healthy controls. About forty per cent of the cystic fibrosis patients had plasma calcitonin levels that were markedly higher than normal. Elevated levels were found predominantly in female patients. In general, patients with marked pulmonary involvement had high plasma calcitonin levels. Immunoextraction and gel chromatography, carried out on plasma of one of the patients demonstrated monomer-like forms of calcitonin similar to those found in the healthy subjects.

Serum calcitonin levels in anesthetized rats

In order to determine whether a short period of general anesthesia influences the levels of serum calcitonin (CTs) and whole blood ionized Ca2+ and pH, 10 rats were sequentially anesthetized at 5-day intervals by halothane, ether, or CO2/O2, respectively, and retroorbital blood samples were collected during anesthesia. We noticed significant differences of serum calcitonin but the role of the anesthetics remains unclear, since other factors also could have accounted for the observed variations. Blood pH was strongly decreased by CO2/O2. Whole blood ionized calcium exhibited marked changes, but no correlation was found between whole blood ionized calcium and serum calcitonin.

Postmenopausal osteoporosis: response of immunoextracted calcitonin to a calcium clamp

Fourteen postmenopausal females with osteoporosis (PMO) and 14 healthy postmenopausal females (PMF) were studied by means of the calcium clamp-technique. Plasma was collected before start and during the 1 hour calcium clamp. Calcitonin (CT) was immunoextracted from plasma with antiserum No. 1 directed against the mid- and carboxyterminal portion of CT. Thereafter radioimmunoassay was performed on the extracts with antiserum No. 2 directed against the carboxyterminal of CT. The detection limit of the assay was 0.8 pg/tube. There was no difference between patients and controls in the basal CT values and CT was detectable in all samples after immunoextraction. Plasma CT increased significantly during the calcium clamp in osteoporotic patients as well as in controls and the CT response did not differ between the groups. The results do not support the hypothesis of a diminished CT secretion as a contributing factor to the development of osteoporosis.

Immunoextracted calcitonin in human gastric secretion

Immunoreactive calcitonin (iCT) has been demonstrated in human gastric juice after immunoextraction with immobilized antibodies and subsequent radioimmunoassay. The basal levels were 4.5 +/- 3.1 (mean +/- SD) pg-Eq/ml gastric juice; range 1.2-9.1 pg-Eq/ml; n = 7, and after stimulatory gastric secretion test with pentagastrin 0.3 +/- 0.2 pg-Eq/ml; range 0.1-0.7 pg-Eq/ml; n = 7 (p less than 0.01). The main fraction of iCT from gastric juice eluted in the same region as synthetic human calcitonin (hCT) on Sephadex G-75 gel chromatography. Reverse phase chromatography in a fast protein liquid chromatography (FPLC) system revealed a slightly less hydrophobic character of the iCT from gastric juice compared to synthetic monomeric hCT. The results were further confirmed by using an additional antiserum. In plasma, the calcitonin (CT) levels were after immunoextraction at the basal state 6.6 +/- 1.7 pg-Eq/ml (mean +/- SD); range 5.1-10.1 pg-Eq/ml; n = 7 and after pentagastrin stimulation 9.4 +/- 5.4 pg-Eq/ml; range 6.3-18.5 pg-Eq/ml; n = 7.

Evidence for precursors of calcitonin/PDN 21 in human milk

Large amounts of immunoreactive PDN-21 (iPDN -21) were found in human milk in concentrations similar to those of immunoreactive calcitonin (iCT): 187 +/- 73 pM (mean +/- S.D.) vs 210 +/- 83 pM. (n = 17). Calcitonin (CT) was immunoextracted from milk by means of CT antibodies coupled to Sepharose 4B, and the extracts were gel-chromatographed on Sephadex G-75 after treatment with 6 M guanidine HCl. iCT and iPDN-21 in the fractions were determined with radioimmunoassay. The main part of iCT eluted as high molecular weight forms and these fractions also contained iPDN-21. Enzymatic cleavage of immunoextracted milk CT by trypsin demonstrated that iPDN-21 could be split apart from the high molecular weight forms and be recovered at the position of synthetic human PDN-21 on gel chromatography. iCT was eluted in the region of monomeric CT and as larger forms. Since PDN-21 constitutes the carboxyterminal of preprocalcitonin, our results indicate that human milk contains precursors of calcitonin.

The influence of sex steroid hormones on plasma calcitonin response to the calcium clamp in normal subjects

The influence of sex steroid hormones on plasma calcitonin levels in healthy subjects was studied in 15 males and 10 premenopausal (PREMF) and 12 postmenopausal females (PMF). A standardized ionized calcium stimulus was achieved by means of the calcium clamp technique, and a sensitive RIA was used to determine immunoreactive CT (iCT) in plasma. Plasma iCT levels increased in response to the calcium clamp with an initial peak at 15 or 30 min. The iCT levels then declined but remained at an elevated level for the rest of the 180-min infusion period in all three groups. In males a positive correlation was found between the serum testosterone levels at 0 min and the estimates for initial iCT response, i.e., the change between 0 and 15 min (r = 0.80, n = 11, p less than 0.01), between 0 and 30 min (r = 0.56, n = 15, p less than 0.05) and between 0 and the maximum value (r = 0.68, n = 15, p less than 0.01). In the two female groups no such correlation was found. Serum 17 beta-estradiol or dehydroepiandrosterone sulfate concentrations were not correlated either to basal iCT levels or to the iCT response to the calcium clamp. PMF had lower levels of 17 beta-estradiol than PREMF (p less than 0.001), while the testosterone levels were similar. The iCT levels and response to the calcium clamp showed no significant difference in the two groups. The results indicate that sex difference in the plasma CT levels may be related to different testosterone levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Melatonin, cortisol, prolactin, and calcitonin secretion in primary hyperparathyroidism before and after surgery

The aim of the present study was to determine the diurnal secretion of melatonin, cortisol, prolactin, and calcitonin during chronic parathyroid hormone-dependent hypercalcemia. Eight women, aged 40-76 years, with primary hyperparathyroidism (PHPT) were studied before and after surgical removal of a parathyroid adenoma. The hormone concentrations in blood were determined at 08, 12, 16, 22, 02, 04, and 06 h. Concomitantly, the excretion of melatonin and cortisol in urine between 07-19 h and 19-07 h, and the clearance of calcium and creatinine were measured. Nyctohemeral serum prolactin and calcitonin were unaffected by moderate parathyroid hormone-dependent hypercalcemia. In contrast, serum cortisol and melatonin were significantly higher during active disease than after surgical cure. Mean 24-h variation of serum cortisol was 349 +/- 34 nmol/liter vs. 223 +/- 17 nmol/liter and mean serum melatonin was 0.13 +/- 0.04 nmol/liter vs. 0.06 +/- 0.02 nmol/liter. Endogenous creatinine clearance was similar before and after surgery, while the clearance of melatonin and cortisol significantly increased after surgery, indicating an increased tubular reabsorption of both hormones during active disease. Fasting morning glucose concentrations were also significantly decreased after successful surgery, 6.1 +/- 0.6 vs. 5.2 +/- 0.5 mmol/liter. It is suggested that the relative hypercortisolism may be the cause of the glucose intolerance in primary hyperparathyroidism. Three to 4 months after surgical cure the serum melatonin levels were significantly lower than those seen in age-matched controls, indicating a melatonin insufficiency in patients successfully treated for PHPT. The meaning of this finding is not yet understood but might be of importance in the development of primary hyperparathyroidism.

Immunoextracted calcitonin in milk and plasma from totally thyroidectomized women. Evidence of monomeric calcitonin in plasma during pregnancy and lactation

The level of immunoreactive calcitonin in the first produced breast milk was in totally thyroidectomized (TX) women 713 +/- 307 pg-eq/ml (mean +/- SD, N = 7) and in control women 772 +/- 329 pg-eq/ml (N = 33), i.e. about 45 times higher than in plasma (see below). On gel chromatography of immunoextracted milk from TX women, immunoreactive calcitonin appeared as high molecular weight forms in the same pattern as in milk from healthy women when the same antiserum was used for immunoextraction and radioimmunoassay (RIA). In another series of experiments, a new antiserum raised in rabbits was used for measurement of immunoreactive calcitonin after immunoextraction with 1. Plasma levels of immunoreactive calcitonin in the TX women during pregnancy were 16 +/- 6 pg-eq/ml (N = 6) and during lactation 14 +/- 7 pg-eq/ml (N = 5). Immunoreactive calcitonin was undetectable (less than 8 pg/ml) in plasma from those TX women in whom lactation had stopped (N = 5). Immunoextraction and gel chromatography of plasma collected during pregnancy and lactation from the TX women showed that the immunoreactive calcitonin present eluted in the region of monomeric calcitonin with both antiserum 1 and 2. In conclusion, high concentrations of high molecular weight forms of of immunoreactive calcitonin have been demonstrated in milk from TX patients, most probably devoid of any calcitonin-producing thyroid C-cells. This points to a local production site in the mammary gland.(ABSTRACT TRUNCATED AT 250 WORDS)

Large forms of immunoreactive calcitonin in human seminal fluid exhibit PDN-21 immunoreactivity

Semen samples were obtained from 4 healthy males on two occasions. One of the samples was liquefied at room temperature for 20 min while the other was diluted immediately with buffer to suppress proteolysis. A pool of immunoextracted calcitonin from liquefied and diluted samples, respectively, was subjected to gel chromatography in a separate experiment. In lyophilized samples the majority of immunoreactive calcitonin (CT) had an approximate molecular weight (Mr) of 10 kilodaltons (Kd) and immunoreactive PDN-21 was also present in the fractions. In diluted ejaculates CT was composed of larger species as well as the 10 Kd form. PDN-21 was present in fractions containing the 10 Kd form but could not be detected in the peaks of larger molecular weight, probably because of lower sensitivity of the PDN-21 assay compared to the CT assay. Our finding of CT and PDN-21 in the same fractions after immunoextraction with CT antibodies suggests the presence of proforms of CT in human seminal fluid.

Immunoextracted calcitonin from human seminal plasma constitutes different forms

Levels of immunoreactive calcitonin (iCT) in human seminal plasma were studied after extraction with immobilized antibodies. Immunoextraction of semen was necessary to abolish the high concentrations of proteolytic enzymes that can interfere in radioimmunoassay (RIA). Since proteolysis occurs already during semen liquefaction, iCT levels and chromatographic properties were compared in extracts from liquefied ejaculates, and samples were the proteolysis was suppressed by immediate dilution of the ejaculates with buffer. The levels in the two groups were 81 +/- 43 pg-equivalents ml-1 seminal plasma (mean +/- SD, n = 6) in liquefied samples and 120 +/- 42 pg-equivalents ml-1 (n = 7) in diluted samples, which is about ten times the iCT levels in extracted blood plasma from healthy males. Extracted liquefied seminal plasma from two vasectomized men contained 93 and 107 pg-equivalents of iCT ml-1 seminal plasma, respectively. Gel chromatography of undiluted semen samples disclosed that iCT was composed of forms larger than monomeric CT, the major part with an approximate molecular weight (MW) of 10,000. Two of the six subjects had a smaller amount of iCT eluting with a MW of about 40,000. In diluted samples, iCT seemed to be more heterogenous with approximate molecular weights ranging from 40,000 to fragments smaller than monomeric CT. In some ejaculates, monomeric CT seemed to be present. Undiluted samples from vasectomized men contained iCT with the same chromatographic pattern as in normal men.

Plasma calcitonin response to a calcium clamp in endogenous Cushing's syndrome

Basal and calcium (Ca) stimulated plasma CT concentrations have been studied in 6 premenopausal females with Cushing's disease and 3 premenopausal females with Cushing's syndrome due to an adrenocortical adenoma. Thirteen healthy premenopausal females served as a reference group. A standardized Ca-stimulus was applied to all subjects by means of the 'calcium clamp' technique. Plasma immunoreactive CT (iCT) was determined by RIA using a carboxyl terminal antiserum with 8 pg-eq/ml as detection limit. The patients with Cushing's disease had normal basal plasma iCT levels and their iCT response during the 2 h calcium clamp was within the reference range in 5 out of 6 patients, the remaining patient showed a slightly exaggerated response. The patients with adrenal adenoma had elevated plasma iCT levels in the basal state but a normal response during the calcium clamp. It is therefore less likely that the bone resorption often seen in Cushing's syndrome is due to CT deficiency.

Gel chromatography of immunoextracted plasma calcitonin in response to the calcium clamp in healthy males

A radioimmunoassay (RIA) was developed for immunoreactive calcitonin (iCT) in human plasma. Antibodies against synthetic human calcitonin (hCT) coupled to bovine serum albumin (BSA) were raised in rabbits and were directed against the carboxy terminal part of CT. The detection limit of the assay was 8 pg/ml. In 7 males the iCT response to a calcium-clamp was studied. Blood was collected at 0, 30 and 60 min after the start of the calcium infusion. iCT was measured directly in plasma and in extracts obtained after purification of plasma iCT by means of immobilized CT antibodies. There was a good correlation between iCT in plasma samples and extracts, r = 0.993, n = 14 (P less than 0.001). Dilution curves of extracts and plasma were parallel with the hCT standard curves. Gel chromatography of the extracts on Sephadex G-50 and G-75 disclosed heterogeneity of iCT in normal plasma during basal conditions as well as during calcium stimulation. Thirty min after the start of the calcium clamp all molecular forms, most likely constituting monomeric and dimeric CT and larger forms, were increased, while after 60 min iCT seemed to constitute predominantly forms larger than monomeric CT. Basal levels of unextracted iCT in healthy males (n = 44, 37 +/- 10 years) were 15 +/- 9 pg-equivalents/ml (mean +/- SD) which was higher than in females (n = 40, 32 +/- 9 years) 11 +/- 4 pg-equivalents/ml (P less than 0.05).

Plasma calcitonin response to a calcium clamp. Influence of sex and age

The influence of sex and age on basal and calcium stimulated immunoreactive plasma calcitonin (iCT) were studied in 36 healthy subjects. An identical calcium stimulus, "calcium clamp", was applied to 10 young males, 13 premenopausal females of similar ages and 13 postmenopausal females. A significantly greater iCT response was found in males compared with both female groups. No age correlation in basal or calcium stimulated iCT levels was observed despite 35 years difference in mean age between the pre- and postmenopausal groups. A positive correlation between the induced change in whole blood ionized calcium (B-Ca++) and the iCT response, recorded after 15 min, was seen in young subjects of both sexes. Basal iCT and B-Ca++ were similar in all three groups. No correlation between basal iCT and basal B-Ca++, or between basal iCT and age was found. The total amounts of infused calcium per kg body weight were equal. The results indicate that male subjects have a greater secretory capacity of the thyroid C-cell than females. No reduction of the secretory capacity was observed with increasing age in females, neither was any difference found between pre- and postmenopausal females of the iCT-response.