Plasma calcitonin in rats with renal failure

To study the effect of the kidney on blood calcitonin (CT), rats were made uremic by either total or partial nephrectomy or bilateral ligation of the ureters. Plasma CT concentrations were measured by radioimmunoassay before and after calcium infusion. Uremia induced by total or partial nephrectomy produced an increase in plasma CT. Rats had higher plasma CT levels (49.3 +/- 1.7 pg/ml, mean +/- SE) after total nephrectomy than after ureteral ligation (30.9 +/- 1.5 pg/ml) even though no significant difference was observed between the blood urea nitrogen (BUN) levels of these two groups. These results indicate that the kidney contributes to the degradation of CT.

The coregulation of secretion and cytoplasmic ribonucleic acid of chromogranin-A and calcitonin by phorbol ester in cells that produce both substances

We have undertaken studies of the regulation of the secretion and cytoplasmic mRNA of chromogranin-A (CgA) and calcitonin (CT) in cells that secrete both substances in order to determine if they are regulated through the same mechanisms. Studies were conducted in cell lines derived from a human medullary thyroid carcinoma (MTC) and a human lung cancer (M103). Treatment with phorbol-12-myristate-13-acetate (PMA) resulted in a dose-dependent increase in the secretion of both CT and CgA by the two cell lines. Phorbol at 1000 nM resulted in 4- and 10-fold increases in CgA secretion and 3- and 5-fold increases in CT secretion by the MTC and M103 cells, respectively. The secretory patterns were similar for CgA and CT. In the M103 cells the same treatment resulted in a 100% increase in CgA-specific cytoplasmic RNA and a 70% increase in CT-specific cytoplasmic RNA. The secretion of CgA and CT was coordinately regulated by phorbol in both MTC and M103 cells, and related mRNA changes could be detected in the M103 cells. These observations support the hypothesis that CT and CgA secretion and gene expression are under similar regulatory controls.

Effects of hypophysectomy and subsequent hormonal replacement therapy on hormonal and osmoregulatory status of coho salmon, Oncorhynchus kisutch

This study investigates the effects of hypophysectomy and subsequent hormone replacement therapy upon the hormonal and osmoregulatory status of coho salmon, Oncorhynchus kisutch, in 7% seawater (SW) and SW. Following hypophysectomy, coho salmon were injected every 2 days for 8 days with thyroxine, growth hormone, and cortisol, alone or in combinations, and sampled 2 days after the final injection. Increased environmental salinity raises plasma sodium, calcium, and magnesium levels, as well as plasma osmolality. Cortisol is hypercalcemic and thyroxine is hypocalcemic in hypophysectomized salmon, but it is unclear whether these effects are due directly to calcium regulation or are the consequence of general effects on the plasma osmotic/ionic balance. Growth hormone and thyroxine together, but not separately, decrease and increase magnesium levels, at low and high environmental salinities, respectively, indicating a complex endocrine control of plasma magnesium. Gill Na+, K+-ATPase activity in hypophysectomized salmon is stimulated by growth hormone and cortisol, but inhibited by thyroxine and raised environmental salinity. This implies a complex endocrine control and indicates that hormonal support is needed to sustain or raise gill Na+, K+-ATPase activity in seawater. Increased environmental salinity induces elevation of plasma cortisol levels in apparent absence of pituitary control, indicating that the interrenals may respond to changes in external and/or internal environment, either directly or indirectly through extrapituitary hormonal or nervous control. Cortisol is a potent inhibitor of calcitonin secretion, as seen by the large decrease in plasma calcitonin levels in cortisol-treated hypophysectomized fish. The study was carried out at a time when thyroxine plasma levels were low. These basal levels were not affected by hypophysectomy, possibly indicating a basal release of thyroxine from the thyroid without stimulatory support of the pituitary gland.

Localization of calbindin-D28K in calcitonin containing cells of chick ultimobranchial glands

Specific antisera raised against calbindin-D28K (CaBP), the vitamin D-dependent calcium-binding protein from chick intestine, was used to localize the protein in chick ultimobranchial glands (UB glands) by the peroxidase-antiperoxidase technique. CaBP was localized in secretory cells in the cell cords and in a few cells of the epithelium lining the follicles. It was not found in the fibroblastlike cells in the cell cords nor in islands of parathyroid tissue present in the UB gland. The immunomarker for CaBP was distributed throughout the cytoplasm and nucleus of the secretory cells. The same cells demonstrated a positive reaction in their cytoplasm when reacted with an antiserum specific for salmon calcitonin (CT), thus confirming the presence of CaBP and CT in the same UB-gland secretory cells. In other tissues, the presence of CaBP is regarded as an end-organ marker for actions of the vitamin D endocrine system. This novel demonstration of CaBP in UB-gland cells responsible for secretion of calcitonin suggests a direct effect of the vitamin D endocrine system on those cells in addition to an indirect effect through the stimulation produced by elevated circulating calcium levels.

Pituitary cells secrete calcitonin in the reverse hemolytic plaque assay

Rat pituitary cells were evaluated in the reverse hemolytic plaque assay for calcitonin (CT) secretion. The secretion of CT could be demonstrated by the formation of hemolytic plaques around single pituitary cells when a specific CT antibody was used. Approximately 0.1 percent of the cells secreted CT in the basal state. Phorbol stimulated CT secretion by up to 25-fold. The diameter of the hemolytic plaques around pituitary cells from genetically obese (Zucker) rats was significantly greater than normal rats (24 versus 37 microns). This study demonstrates that pituitary cells secrete CT and that the secretion may be regulated by pharmacological agents (phorbol) and physiological signals (obesity).

Chromogranin A is present in and released by fish endocrine tissue

Chromogranin A (CgA) is a protein that is present in many mammalian endocrine cells and co-secreted with their resident hormones. We have demonstrated the presence of CgA by immunohistology in the ultimobranchial glands and corpuscles of Stannius of rainbow trout. CgA was also detected by radioimmunoassay in the medium of incubated coho salmon ultimobranchial glands. Our observations demonstrate the presence of CgA in endocrine glands of evolutionarily divergent species. These observations are consistent with the hypothesis that CgA participates in the secretory process of a wide variety of hormones.

The gene for human chromogranin A (CgA) is located on chromosome 14

Chromogranin A (CgA) is a protein that is present in most neuroendocrine tissues and is co-secreted with their resident hormones. We have assigned the CgA gene to human chromosome 14 by hybridization of a CgA cDNA probe cloned from a cDNA library of human medullary thyroid carcinoma cells to spots of individual human chromosomes flow-sorted onto nitrocellulose filters. Southern analysis of human genomic DNA with the same probe revealed only 1-3 restriction bands. These studies indicate that the CgA gene is probably single copy and not a member of a dispersed, multigene family. The CgA gene is not co-localized with the genes of any of the CgA-associated hormones.

Effects of dietary calcium and age on parathyroid hormone, calcitonin and serum and milk minerals in the periparturient dairy cow

Ten pregnant heifers and 10 pregnant cows (three or more pregnancies) were assigned to groups of five and fed either the recommended (low) amount of calcium or excess (high) calcium in their diet for 4 wk before parturition to determine the influence of prepartum calcium intake and age on hormonal control of peripartum calcium homeostasis. After parturition all groups received a diet with calcium adequate for lactation. Jugular blood samples from 21, 14, 7, 6, 5, 4, 3, 2, and 1 d prepartum through 0, 1, 2, 3, 5, 7, 14 and 21 d postpartum were assayed for concentration of parathyroid hormone, calcitonin, calcium, magnesium and phosphorus. Heifers and cows receiving high calcium diets had higher calcium and lower parathyroid hormone in blood serum before parturition than animals receiving the low calcium diets. Cows, but not heifers, fed high calcium diets exhibited severe hypocalcemia at parturition, remained hypocalcemic for 3 d and had low serum calcitonin. Regardless of dietary group, concentrations of parathyroid hormone and magnesium in serum increased after the first week of lactation. Feed intake during lactation, corrected for metabolic body weight, was similar for both dietary treatments and ages. Milk production per kilogram metabolic body weight was highest during the first week of lactation for cows fed low calcium diets before parturition. There was no correlation between hypocalcemia and loss of calcium in colostrum or milk. Feeding low dietary calcium to cows in the prepartum period was effective in the prevention of severe hypocalcemia at parturition. In contrast, dietary treatment of heifers had no effect on serum calcium concentration at parturition.(ABSTRACT TRUNCATED AT 250 WORDS)

Elevated serum chromogranin A concentrations in small-cell lung carcinoma

Serum chromogranin A concentrations measured by radioimmunoassay in patients with small-cell lung carcinoma were compared with values from healthy adults and patients with non-small-cell lung carcinoma or chronic obstructive pulmonary disease. The mean (+/- SE) level was significantly higher (p less than or equal to 0.02) in patients with small-cell lung carcinoma (815 +/- 290 ng/mL, n = 46) than in normal controls (123 +/- 6 ng/mL, n = 20) or patients with chronic obstructive pulmonary disease (169 +/- 18 ng/mL, n = 39), lung adenocarcinoma (180 +/- 22, ng/mL, n = 62), large-cell lung carcinoma (183 +/- 23 ng/mL, n = 18), or lung epidermoid carcinoma (203 +/- 37 ng/mL, n = 78). The mean concentration in extensive-stage small-cell lung carcinoma (1155 +/- 449 ng/mL, n = 29) was significantly greater (p = 0.026) than in limited disease (234 +/- 56 ng/mL, n = 17). Elevated serum chromogranin A values were seen in 53% of patients with limited and 72% with extensive disease. Four patients originally classified as having non-small-cell lung carcinomas with raised chromogranin A levels were subsequently found to have mixed small-cell and non-small-cell tumors. Serum chromogranin A concentrations may be a useful marker of small-cell lung carcinoma disease activity.

The antiproliferative effect of calcitriol on human peripheral blood mononuclear cells

Activation of lymphocytes leads to the expression of receptors for the calcitropic hormone calcitriol [1,25(OH)2D3], and calcitriol is a potent inhibitor of interleukin-2 (IL-2) and of lymphocyte proliferation. We used peripheral blood mononuclear cells (PBM) activated in vitro with phytohemagglutinin to study 1) the relationship between 1,25(OH)2D3 receptor expression, IL-2 production, and 1,25(OH)2D3-induced inhibition of PBM proliferation in connection with the cell cycle; 2) the effect of 1,25(OH)2D3 on PBM activation and on the expression of activation-related molecules including the IL-2 receptor, and 3) the role of calcium in the antiproliferative effect of the hormone. 1,25(OH)2D3 receptor expression occurred when PBM entered the G1a phase of the cell cycle. The concentration of the receptor protein reached a peak at G1b and declined during the S phase. 1,25(OH)2D3 inhibited cell proliferation by blocking PBM at the G1a-G1b border. The antiproliferative effect of calcitriol was not caused by hormonal interference with the calcium-dependent activation process nor with the expression of activation-related molecules including the IL-2 receptor. Moreover, this effect was not influenced by extracellular calcium, suggesting that the hormonal action cannot be due to calcium translocation. These findings support the contention that 1,25(OH)2D3-induced inhibition of PBM proliferation is mediated through selective inhibition of IL-2 production.

Calcium-regulating hormones across the menstrual cycle

Midcycle elevations of serum PTH, calcitonin (CT), and 1,25-dihydroxyvitamin D [1,25-(OH)2D] in women have been reported. To examine the effects of cyclic changes in ovarian steroid secretion on calcitropic hormone concentrations, we used a cytoreceptor assay for 1,25-(OH)2D and homologous RIAs for PTH and CT to measure these hormones in daily blood samples obtained from six women throughout the menstrual cycle. Significant changes in serum PTH, CT, 1,25-(OH)2D, calcium, and phosphorus concentrations during the cycle were not found; transverse means (+/- SE) were 101 +/- 3.5 pg/ml for PTH, 30.8 +/- 1.8 pg/ml for CT, and 40.1 +/- 1.7 pg/ml for 1,25-(OH)2D. In addition, CT reserve was assessed by calcium infusion (3 mg/kg, iv, in 10 min) during the early and late follicular and midluteal phases of the cycle. Although serum CT increased significantly (P less than 0.01) after calcium infusion, the mean (+/- SE) increment (23.2 +/- 2.2 pg/ml) did not significantly differ in the three phases of the cycle (early follicular, 23.8 +/- 4.0; late follicular, 23.3 +/- 3.4; midluteal, 22.5 +/- 4.1). Our data do not support previous reports of midcycle elevations in serum PTH, CT, and 1,25-(OH)2D concentrations, and we conclude that serum concentrations of the calcitropic hormones do not significantly vary during the menstrual cycle.

A cloned chromogranin A (CgA) cDNA detects a 2.3Kb mRNA in diverse neuroendocrine tissues

CgA is a 72Kd protein of unknown function that is present in many neuroendocrine tissues and co-secreted with their resident hormones. We prepared a cDNA library to the mRNA from CgA-producing human medullary thyroid carcinoma (MTC) cells in the expression vector lambda gt11. The library was screened with a panel of one polyclonal and two monoclonal antibodies to CgA. The specificity of the antibodies for CgA was demonstrated by immunoassay, immunohistology, and immunoprecipitation of the in vitro translation products of mRNA from CgA-producing tissues. A chromogenic second antibody identified five immunoreactive clones. Their cDNA inserts were isolated after EcoRI digestion and agarose gel electrophoresis. These cDNAs were 32P-labelled and used as probes in Northern hybridization studies. An mRNA of approximately 2.3Kb was detected with the cDNA probes in human cell lines from MTC and lung cancers that were shown to produce CgA and in human pheochromocytoma and bovine adrenal medulla tissue. To confirm its identity, one of the putative CgA cDNAs was subcloned into a plasmid and was used to hybridization-arrest the in vitro translation of CgA mRNA. These studies demonstrate the cloning of cDNAs which hybridize with CgA mRNA from diverse neuroendocrine tissues.

Secretion of chromogranin A by peptide-producing endocrine neoplasms

Chromogranin A, the protein that is co-stored and co-released with catecholamines from the adrenal medulla, has recently been identified in a variety of human endocrine tissues, both normal and neoplastic. We investigated the secretion of chromogranin A by peptide hormone-producing human tumors in studies of patients with the following neoplastic disorders: pheochromocytoma, parathyroid adenoma, primary parathyroid hyperplasia, medullary thyroid carcinoma, thyroidal C-cell hyperplasia, carcinoid tumor, oat-cell lung carcinoma, pancreatic islet-cell tumor, and aortic-body tumor. All these patient groups had elevated concentrations of plasma chromogranin A. We distinguished different forms of immunoreactive plasma chromogranin A by size with the use of gel filtration. Plasma chromogranin A levels were not elevated in patients with diverse "control" conditions--both benign and malignant and both endocrine and nonendocrine--in which peptide hormones are not produced. The sensitivity and specificity of plasma chromogranin A elevations in the diagnosis of peptide-producing endocrine neoplasms were 81 and 100 percent, respectively. The elevation of plasma chromogranin A in our subjects suggests that their neoplasms co-release chromogranin A along with the usual resident hormone of the tumor, that these neoplasms could be characterized as "chromograninomas," and that measurement of plasma chromogranin A may be a useful diagnostic procedure in subjects with endocrine tumors, especially multiple endocrine neoplasia.

1 alpha,25-Dihydroxyvitamin D3-binding macromolecules in human B lymphocytes: effects on immunoglobulin production

Previous studies have indicated that upon in vitro activation with mitogenic lectins, human peripheral blood T lymphocytes express receptors for the steroid hormone 1 alpha, 25-dihydroxyvitamin D3(1,25(OH)2D3). Furthermore, the hormone can inhibit interleukin 2 production by the activated cells. In this investigation, we report that human peripheral B lymphocytes activated in vitro with the B lymphotropic Epstein-Barr virus (EBV) also express 1,25(OH)2D3 receptor-like macromolecules. These receptors are localized in the cell nucleus and exhibit properties similar to those found in classical target tissues for 1,25(OH)2D3. They sediment on sucrose gradients at 3.3 S, display a dissociation constant (Kd) of 4 X 10(-10) M, and can bind to DNA. In addition to the 1,25(OH)2D3 receptors, however, EBV-activated lymphocytes express a second class of 1,25(OH)2D3-binding proteins that appear to occur mainly in the cell cytosol and exhibit distinct biochemical properties from the receptor, including higher sedimentation coefficients (3.7 S to 4 S) and the lack of ability to bind to DNA. The addition of 1,25(OH)2D3 to cultures of EBV-infected cells inhibited the production of IgM and IgG by the B cells. The vitamin D3 analog 24,25(OH)2D3 did not inhibit Ig production, thus suggesting that the effect is probably mediated through the high affinity receptor macromolecule localized in the nucleus. Because the EBV-induced Ig production is independent of T cell participation, the data also suggest that the effects of 1,25(OH)2D3 are exerted directly on the B cell. The present results add to the evidence of the importance of 1,25(OH)2D3 as an immunoregulatory hormone.

1 alpha,25-Dihydroxyvitamin D3-binding macromolecules in human B lymphocytes: effects on immunoglobulin production

Previous studies have indicated that upon in vitro activation with mitogenic lectins, human peripheral blood T lymphocytes express receptors for the steroid hormone 1 alpha, 25-dihydroxyvitamin D3(1,25(OH)2D3). Furthermore, the hormone can inhibit interleukin 2 production by the activated cells. In this investigation, we report that human peripheral B lymphocytes activated in vitro with the B lymphotropic Epstein-Barr virus (EBV) also express 1,25(OH)2D3 receptor-like macromolecules. These receptors are localized in the cell nucleus and exhibit properties similar to those found in classical target tissues for 1,25(OH)2D3. They sediment on sucrose gradients at 3.3 S, display a dissociation constant (Kd) of 4 X 10(-10) M, and can bind to DNA. In addition to the 1,25(OH)2D3 receptors, however, EBV-activated lymphocytes express a second class of 1,25(OH)2D3-binding proteins that appear to occur mainly in the cell cytosol and exhibit distinct biochemical properties from the receptor, including higher sedimentation coefficients (3.7 S to 4 S) and the lack of ability to bind to DNA. The addition of 1,25(OH)2D3 to cultures of EBV-infected cells inhibited the production of IgM and IgG by the B cells. The vitamin D3 analog 24,25(OH)2D3 did not inhibit Ig production, thus suggesting that the effect is probably mediated through the high affinity receptor macromolecule localized in the nucleus. Because the EBV-induced Ig production is independent of T cell participation, the data also suggest that the effects of 1,25(OH)2D3 are exerted directly on the B cell. The present results add to the evidence of the importance of 1,25(OH)2D3 as an immunoregulatory hormone.

Measures of bone loss in rheumatoid arthritis

Patients with rheumatoid arthritis (RA) are prone to develop osteoporosis, especially women receiving steroid hormone therapy. Inhibition of bone formation and/or excessive bone resorption may be responsible. Bone gamma-carboxyglutamic acid-containing protein (BGP), the major noncollagen protein of bone and a plasma marker of bone formation, was measured in 81 consecutive RA patients and 79 age- and sex-matched control subjects, in addition to the hormone regulators of bone metabolism, calcitonin, parathyroid hormone, and 1,25-dihydroxyvitamin D. Mean (+/- SE) BGP levels (picomoles per milliliter) were lower for RA men (1.46 +/- 0.14) and women (1.52 +/- 0.2) compared with their respective controls (2.05 +/- 0.17 for men, 2.47 +/- 0.22 for women). Women taking steroids had the lowest levels (1.13 +/- 0.22) and, in contrast to men, this value was lower than the nonsteroid-treated group. Steroid treatment appears to be a major determinant of low BGP levels; the effect of RA itself is suspected but not proved in this study. Calcitonin levels were lower in RA men as well as in all women. Diminution of BGP in these subjects supports the view that "low-dose" corticosteroid treatment may suppress bone formation, especially in women. Prevention or remediation of osteopenia may be monitored by BGP, if further studies validate this hypothesis with other measures of skeletal mass.

1,25-Dihydroxyvitamin D3 promotes in vitro morphologic and enzymatic changes in normal human monocytes consistent with their differentiation into macrophages

1,25-dihydroxyvitamin D3 [1,25(OH)2D3] has been shown to promote the in vitro differentiation of established human monocytic cell lines and normal human bone marrow progenitor cells toward the macrophage phenotype. The possibility that 1,25(OH)2D3 exerts a similar effect on the differentiation of peripheral monocytes from normal individuals, has been examined in the present study. Monocytes were isolated by density gradient sedimentation on Ficoll-Paque followed by adherence to plastic. Cells were subsequently maintained in culture in 10% autologous serum for 4 weeks either with or without 1,25(OH)2D3 (10(-8) M). In five experiments using monocytes from different donors we found that cells grown in the absence of the hormone underwent morphologic changes toward the macrophage phenotype as well as a gradual increase in the activities of lysosomal enzymes (beta-acetyl-glucosaminidase and beta-galactosidase). In the presence of the hormone the morphologic changes appeared at earlier stages of the culture, and the increase in enzymatic activities occurred earlier and was one- to twofold greater than the activity of the control cells. In addition, 1,25(OH)2D3 enhanced the adherence of the cultured cells.

The involvement of calcitonin in the reproductive physiology of the rainbow trout

Plasma from rainbow trout (Salmo gairdneri) of both sexes was sampled every month throughout an annual reproductive cycle in order to elucidate possible relationships between plasma calcitonin and free and protein-bound calcium and magnesium. This was then studied in greater detail around the time of ovulation in the female fish. The plasma levels of the parameters studied were stable in males during the whole annual cycle and were similar to the levels found in females during at least 6 months of the cycle. Plasma levels of protein-bound calcium and magnesium as well as calcitonin were raised in the females for 6, 4 and 3 months respectively. These increases occurred concomitantly during the months before and after ovulation, but no correlations between the protein-bound ion and calcitonin levels were found during this period. With the exception of a decrease observed in December, the free plasma levels of calcium and magnesium were stable in both males and females throughout the cycle. This decrease was attributed to the high production rate of the yolk-protein precursor vitellogenin, which binds both calcium and magnesium. In the detailed study on the ovulating females, plasma calcitonin levels were high 4 weeks before, and continued to increase until the time of ovulation, when a sharp decrease towards normal was noted. The free plasma calcium and magnesium levels were not affected, while the protein-bound levels of calcium and magnesium were found to decline towards normal for the duration of the experiment, without any obvious correlation with the time of ovulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Imparied calcitonin secretion in patients with Williams syndrome

Williams syndrome is associated with neonatal hypercalcemia of unclear pathogenesis. To learn more about the hormonal control of calcium metabolism in patients with Williams syndrome, we studied five such children, with intravenous calcium and parathyroid hormone infusions as provocative stimuli. These patients were found to have significantly higher mean baseline calcium concentrations, delayed clearance of calcium after intravenous calcium loading, and blunted calcitonin responses after calcium infusion, compared with a group of seven normal children. No abnormalities of vitamin D metabolite concentrations were found, either before or after parathyroid hormone stimulation. Our studies demonstrate that patients with Williams syndrome have a defect in the synthesis or release of immunoreactive calcitonin. A deficiency of calcitonin may explain the abnormalities of calcium metabolism seen in these patients and can serve as an important endocrine marker for Williams syndrome.

Hypercalcemia in rats bearing growth hormone- and prolactin-secreting transplantable pituitary tumors

We evaluated the effects of chronic massive elevations of serum GH and PRL on calcium metabolism in rats bearing the MStT/W15 and 7315a transplantable pituitary tumors. MStT/W15 tumor rats manifest elevated serum GH and PRL levels, hypercalcemia, hypercalciuria, and elevated serum levels of PTH and 1,25-dihydroxyvitamin D. The hypercalcemia was not reversed by dexamethasone or propranolol treatment, but was ameliorated by starvation. Parathyroidectomy produced hypocalcemia in the MStT/W15 tumor rats, confirming the parathyroid dependence of the hypercalcemia. The 7315a tumor produced a milder degree of hypercalcemia, along with elevated serum levels of PRL, ACTH, and corticosterone; serum GH was normal. In high concentrations, PRL and/or GH may stimulate the secretion of PTH as well as enhance dietary calcium absorption, in part through the mediation of 1,25-dihydroxyvitamin D.

Metabolism of calcium and phosphorus during pregnancy and lactation in white-tailed deer

The effects of pregnancy and early lactation on blood parameters were studied in 4 white-tailed does in 1981-82 and 8 in 1982-83. No year or fecundity effects (P less than 0.05) were found on plasma calcium (Ca), inorganic phosphorus (P), calcitonin (CT), parathyroid hormone (PTH), or oestradiol -17 beta (E2). An increase (P less than 0.05) in dry matter and metabolic feed intake occurred during pregnancy and lactation. Plasma Ca tended to increase during pregnancy and peaked 5-7 weeks pre-partum, while hypocalcaemia was observed 1-2 weeks pre-partum. Elevated concentrations of plasma Ca and P were found during lactation. During the last trimester of pregnancy, plasma concentrations of alkaline phosphatase (AP), PTH, and E2 but not of CT were higher (P less than 0.05) than in the other trimesters. The results indicate a physiological hyperparathyroidism in pregnant deer. Plasma concentrations of CT were higher (P less than 0.05) during lactation and post-weaning than during pregnancy. Increased AP and PTH during late pregnancy may be responsible for Ca absorption and mobilization, whereas elevated plasma concentrations of E2 may function to block excessive bone resorption. After parturition, lowered E2 may allow bone resorption to proceed, relatively high PTH may enhance Ca absorption and mobilization, and elevated CT may protect the skeleton against excessive bone resorption.

Bone turnover in male puberty: a longitudinal study

In a longitudinal study of male puberty, 18 boys were examined every 3 months for at least 2 years. Serum bone Gla protein (BGP), a biochemical marker of bone formation, was determined and related to changes in serum testosterone (T), serum alkaline phosphatase (AP), serum calcitonin, and bone mineral content (BMC). The data demonstrate a steep increase in serum T during puberty (P less than 0.001), with an almost concomitant increase in serum BGP (P less than 0.001) and serum AP (P less than 0.001). Ten months after the maximal increase in serum T, the increase in BMC reached its maximum, whereas there was no significant change in the serum calcitonin. The data demonstrate that the steep increase in serum T during puberty, directly or indirectly, produces acute stimulation of bone formation (estimated from BGP and AP) followed by a highly significant increase in the integrated measurement of bone apposition (BMC).

Calcitonin produces hypercalcemia in leopard sharks

Calcitonin was detected by RIA in sera from four marine species, leopard sharks (Triakis semifasciata), horn sharks (Heterodontus francisci), thornback rays (Platyrhinoides triseriata), and kelp bass (Paralabrax clathratus). These animals have levels of calcitonin and calcium higher than freshwater and terrestrial species have. The administration of salmon calcitonin to bass (4 micrograms/kg BW) produced hypocalcemia and hypophosphatemia as has been reported for other bony vertebrates. In marked contrast, calcitonin produced a prompt hypercalcemia in sharks; the average was 9.8% increase in serum calcium in nine animals with no attendant change in phosphorus. These findings demonstrate that calcitonin can increase serum calcium in sharks. Because shark skeleton is composed of cartilage, this hypercalcemic effect of calcitonin does not require a bony skeleton.

Salmon calcitonin-like immunoactivity in extracts of Tetrahymena pyriformis

Acid extracts of Tetrahymena pyriformis, a ciliated protozoan grown in defined medium revealed the presence of materials with salmon-type calcitonin immunoactivity. These findings add support to earlier reports of the presence of materials closely resembling vertebrate peptide hormones in unicellular microbes.