Porcine Calcitonin Research Articles

Calcitonin in Metabolic Disorders

This chapter discusses calcitonin in metabolic disorders. The balance between mineral deposition and mineral solubilization at the vast interphase between bone and extracellular fluid is quantitatively the predominant factor in the regulation of calcium levels in extracellular fluid and blood. The first submammalian species of calcitonin to be isolated and structurally defined was salmon calcitonin, which was extracted from ultimobranchial tissues and was resolved into three different hormones after purification. The pure human and the porcine hormones are adequate antigens and induce high titers of neutralizing antibodies, especially when given with impurities or conjugated to other proteins. Chemical modification of porcine calcitonin does not impair its immunogenicity despite total or nearly total loss of biological activity. Immunological evaluation of fragments of porcine and human calcitonin molecules suggests that major antigenic determinants are associated with the portion of the peptide extending from residues. The C-terminal amide group, although not essential for full biological activity, is important in immunogenicity.

Calcitonin inhibition of vitamin D-induced intestinal calcium absorption.

Isolated vascularly perfused rat small intestines were maintained for a 4 hr period during which intestinal calcium absorption was measured. Using this system it was demonstrated that intestines from vitamin D-deficient rats exhibit a low rate of calcium absorption. This rate is approximately doubled in intestines from rats which had received vitamin D. An acute infusion of 10 mMRC U of purified porcine calcitonin (CT) into the arterial perfusate produces an immediate drop in calcium absorption in intestines from rats given vitamin D, but has no effect on calcium absorption of intestines from vitamin D-deficient rats. A chronic infusion of 1.25 mMRC U of CT/hr steadily lowers calcium absorption of intestine from rats given vitamin D until the vitamin D deficient level is reached. In contrast to the effect of low levels of CT, an acute infusion of 500 mMRC U of CT produces a large increase in the calcium absorption of intestines from rats which had received vitamin D. This pharmacological effect of large a...

Effect of calcitonin on experimental osteolathyrism. (II). Action of calcitonin on collagen metabolism.

In order to study the effect of calcitonin on the bone collagen metabolism in osteolathyrism, male Wistar rats were placed on 0.1% aminoacetonitrile diet for 9 days. Porcine calcitonin dissolved in gelatin was concurrently administered in a dose of 0.1 MRC U/100g body weight for 8 days and on the 9th day 0.75 MRC U/100g body weight was given 3, 2 and 1hr respectively before sacrifice. Both bone collagen formation and maturation were examined by the determination of specific and total activities of 3Hhydroxyproline in bone collagen, and collagen resorption was examined by the estimation of the amount of hydroxyproline released into the incubation medium from metaphyses. Treatment of lathyritic rats with calcitonin diminished the concentration of serum calcium, phosphate, and rate of collagen resorption, but did not affect collagen formation and collagen maturation. Inhibitory effect of calcitonin on collagen resorption was more pronounced in osteolathyrism than under normal condition. It seemed that parathyroid glands did not play a vital role in the collagen resorption induced by osteolathyrism, since the resorption was not affected by parathyroidectomy. On the other hand, administration of calcitonin (every 0.8 MRC U/rat, 60 and 30min before sacrifice) also counteracted collagen resorption which was induced by low calcium diet and treatment with parathyroid hormone (PTH, 70 USP units).It is concluded that the effect of calcitonin on collagen metabolism resulted in primary inhibition of collagen resorption in osteolathyrism, and that calcitonin counteracted both PTH-dependent collagen resorption and PTH-independent collagen resorption induced by osteolathyrism.

Serum calcium and gastric secretion in chronic gastric fistula rat: influences of parathyroid hormone and calcitonin.

Abstract. The influence of the serum calcium level and of the hormones regulating it, parathyroid hormone (PTH) and calcitonin (CT), on gastric secretion has been studied in the intact, parathyroidectomized (PTX) and thyro‐parathyroidectomized (TX‐PTX) chronic gastric fistula rat. The following test substances have been administered: CaCl2, bovine parathyroid hormone, Na2‐EDTA and porcine calcitonin. An increase of the serum calcium level caused a marked inhibition of gastric secretion, the parathyroid hormone did not show any effect without changes of the calcium level. Calcium decreases after EDTA as well as after calcitonin were also followed by a reduction of gastric secretion. There was no significant difference demonstrable between the intact, PTX‐and TX‐PTX‐animals. The calcitonin effect could be compensated by calcium substitution. A direct influence of PTH and CT on gastric secretion was not detectable; the hormones only exerted indirect effects via the changes of the serum calcium level they induced.

Renal effects of calcitonin and parathyroid extract in man. Studies in hypoparathyroidism.

To clarify the controversial renal action of calcitonin (CT) and a possible interrelationship between CT and parathyroid hormone, eight patients with untreated surgical hypoparathyroidism were studied. Various calcitonins, i.e. extracted porcine, synthetic porcine, synthetic human, and synthetic salmon CT in doses of 150 Medical Research Council U or 1.5 mg were infused over a 3 hr period. Subsequently, six of the same subjects received 500 USP U parathyroid extract (PTE) (Eli Lilly & Co., Indianapolis, Ind.) in 3 hr and later a combination of CT and PTE. In addition, two patients were given an infusion of ammonium phosphate with the aim of producting a phosphaturia of comparable degree as seen after CT and PTE, thus differentiating hormonal from nonhormonal influences on cation excretion. A protocol of serial clearance (C) studies using the patients as their own controls was followed. Serum and urinary inorganic phosphate (P), calcium (Ca), magnesium (Mg), sodium (Na), potassium (K), and creatinine (Cr) were determined and the clearance values calculated. All CT peptides caused a uniform, immediate and significant increase of C(P), C(Na), C(K), C(Ca), and C(Mg), PTE evoked a rise of C(P), C(Na), and C(K), but C(Ca) and C(Mg) were reduced, the Ca and Na figures being not statistically significant. The administration of both CT and PTE resulted in a summation of individual hormone effects on Ca and Mg excretion. Phosphate infusion on the other hand induced an isolated phosphaturia but no concomitant changes of the urinary cations.The hypoparathyroid data demonstrate that calcitonin enhances urinary elimination of P, Na, K, Ca, and Mg independently of parathyroid action, CT and PTE act qualitatively similarly on P, Na, and K excretion, while an antagonism seems to exist for the renal handling of Ca and Mg.

Prolactin, calcitonin and blood calcium in the toads Bufo boreas and Bufo marinus

Bufo boreas and B. marinus show a hypocalcemic response to a single injection of porcine calcitonin (significant in the latter). Chronic treatment results in hypercalcemia. Ovine prolactin treatment results in a tendency toward hypercalcemia in all cases, which was not significant in any single experiment. However, a possible prolactin-ultimobranchial relation remains equivocal.

THE RENAL EFFECTS OF CALCITONIN IN PATIENTS WITH HYPOPARATHYROIDISM

The reported results concerning the effect of calcitonin on the kidney in man have been controversial. In the presence of the parathyroid glands it is impossible to evaluate whether the changes in the renal excretion pattern depend upon a direct action of cal-citonin on the kidney or an indirect stimulation of the parathyroids. To rule out the effect of the parathyroid hormone, we therefore followed the blood levels and the urinary excretion of calcium, magnesium, phosphate, sodium, and potassium in 4 hypo-parathyroid patients, given a single injection of 100 MRC U of porcine calcitonin.

Effects of porcine calcitonin on calcium metabolism in osteoporosis.

ABSTRACT The effect of the administration of porcine calcitonin together with dietary Ca and P supplements for a period of 3 months to 7 osteoporotic patients was evaluated by means of clinical observation, Ca-balance studies, kinetic tracer studies, and neutron activation analysis. Clinical improvement was evidenced in this study by a decrease in back pain and a cessation of spontaneous fractures. The compartmental analysis and the balance studies indicated a decrease in the resorption rate, and a small increase in the Ca balance. Direct measurement of total body calcium by in-vivo neutron activation analysis also showed a small increase in the calcium concentration in the skeleton of several of the patients. Taken by themselves, the objective data are not highly significant, but together with the clinical findings, they suggest a potential efficacy of calcitonin therapy. The three month period studied appears to be insufficient for the accumulation of significant amounts of calcium. The direction of the...

Acute effects of synthetic porcine calcitonins on the renal excretion of magnesium, inorganic phosphate, sodium and potassium.

SUMMARY Synthetic porcine calcitonin (α-calcitonin) and its methionine-sulphoxide derivative (β-calcitonin) were given by intravenous infusion to conscious male rats. α-Calcitonin inactivated by performic acid oxidation was used as a control. Microgram doses of α-calcitonin produced a dose-dependent decrease in the renal excretion of magnesium. The effect was not due to a secondary release of parathyroid hormone since it was also seen in parathyroidectomized animals. A marked increase in the renal excretion of inorganic phosphate, sodium and potassium preceded the change in magnesium excretion in parathyroidectomized rats. It is concluded that the phosphaturia and natriuresis previously described after administration of extracted calcitonin preparations are true effects of the hormone. The effect of β-calcitonin was indistinguishable from that of α-calcitonin.

Stability of fetal calcium levels and bone metabolism after maternal administration of thyrocalcitonin.

The effect of porcine thyrocalcitonin (TCT) upon fetal calcium metabolism was studied in pregnant rats. Pregnant and nonpregnant rats received 75 μCi 47Ca (0.45 mg Ca) intravenously followed by intramuscular administration of 25.4 MRC units TCT (Armour) 5½ hr later. The disappearance curve of the isotope from the maternal plasma and the alterations in plasma specific activity (SA) within an 8-hr period were determined. Those pregnant rats receiving 47Ca plus TCT showed an acute elevation in the plasma SA of 47Ca within 1 hr and a decrease in total plasma calcium from 10.31 ± 0.10 to 7.62 ± 0.70 mg/100 ml, while nonpregnant rats were only mildly responsive to TCT. It is suggested that the high rate of bone resorption during pregnancy potentiates the response to TCT. Isotope disappearance rates for pregnant rats at 20 days of gestation were nearly identical with those for nonpregnant females. Disappearance of 47Ca from fetal plasma and amniotic fluid was not altered by maternal administration of TCT. Howeve...

Ultrastructural localization of calcitonin in the parafollicular cells of pig thyroid gland with cytochrome c-labeled antibody fragments.

Parafollicular cells in mammalian thyroid glands are thought to be responsible for the secretion of calcitonin. In this study, calcitonin was localized in pig thyroid gland by an indirect immunocytochemical technique using rabbit antiserum directed against synthetic porcine calcitonin for the first step, and sheep Fab fragments prepared against rabbit Fab and coupled to cytochrome c for the second step. The antigenic determinants of calcitonin were present only in the parafollicular cells, whose secretory granules were heavily labeled. Labeling of the cytoplasmic matrix is thought to indicate a possible leakage of the polypeptide from the granules. A striking observation was the complete absence of labeling in the cisternae of the rough-surfaced endoplasmic reticulum and of the Golgi apparatus. It is concluded that the secretory granules of parafollicular cells contain calcitonin; the mechanism of synthesis of this peptide is not clearly understood.

Plasma kinetics and acute effects of pharmacologic doses of porcine calcitonin in man.

ABSTRACT Plasma kinetics of a pharmacologic dose of porcine calcitonin (PCT) in man were investigated using a sensitive radioimmunoassay. A single intravenous injection of 1 mg of homogeneous PCT was given to 21 subjects (5 normal, 6 with osteoporosis, 5 with hyperparathyroidism and 5 with Paget's disease) and a continuous prolonged infusion was given to 5 normal subjects. Plasma disappearance after single injection or continuous infusion could be described as a sum of at least 2 exponential components with half-times of 2.4 (0.3) and 40.9 (6.2) min (mean and se). Metabolic clearance rate during continuous infusion was 846 (42) ml/min. The apparent volume of distribution was 21.4 (2.0)% of body weight. Substantial hypocalcemia was associated, in 4 of 5 patients with Paget's disease, with an increase in serum immunoreactive parathyroid hormone (iPTH) which was sustained for the duration of the hypocalcemia; in the other groups these responses were equivocal or absent. However, injection of homogeneous PCT ...

Explanation for unusual potency of salmon calcitonin.

THE calcitonins are polypeptide hormones of thirty-two amino-acids which lower serum calcium in mammals by inhibiting bone resorption1. During evaluation of these hormones as a means of treating skeletal disorders in man, particularly Paget's disease of bone2, 3, the surprising observation was made that calcitonin from the salmon (SCT) is 20–200 times more potent than porcine calcitonin (PCT) and at least ten times more potent than human calcitonin3, 4. SCT is far more potent than any mammalian calcitonin yet tested in a wide variety of animal species5, 6. This unusual potency of salmon calcitonin could reflect either a greater hormone affinity for receptor sites or a greater resistance to metabolic destruction. We now report evidence which supports the latter possibility, infused SCT disappears from the circulation of the dog much more slowly than does PCT.

Secondary hyperparathyroidism produced in kittens repeatedly given porcine calcitonin.

Calcitonin was administered to kittens for periods of 5–10 days; thereafter serial determinations of the serum calcium and phosphorus were made. Subsequently, groups of animals were nephrectomized or thy ropara thyroidectomized; the response to calcitonin was then measured. Calcitonin produced hypocalcemia and hypophosphatemia initially; resistance to the hypocalcemic effect soon developed and was associated with an increasing hypophosphatemic response. The hypophosphatemic response to calcitonin was abolished within 24 hr after nephrectomy or thyroparathyroidectomy. Thyroparathyroidectomy abolished the return to normocalcemia. The results suggest increased parathyroid activity. Autoradiography and tetracycline labeling showed that both endochondral and diaphyseal bone formation rates were suppressed; linear bone apposition rates correlated with the fall in serum phosphorus. Increased osteoclastic activity associated with bone resorption was probably a manifestation of increased parathyroid activity. The ...

Response of plasma Ca to thyroidectomy and calcitonin in growing pigs.

Plasma Ca concentration of intact and thyroidectomized young pigs was measured before and after intravenous administration of porcine calcitonin. Calcitonin (0.2 or 0.4 mg per kilogram body weight) significantly decreased plasma Ca concentration in both intact and thyroidectomized pigs in each of three experiments. The hypercalcemic response to calcitonin was similar in both groups. There was no significant difference in plasma Ca concentration between intact and thyroidectomized pigs before calcitonin administration when pigs were not fasted (Experiments 1 and 3) but in fasted pigs (Experiment 2) thyroidectomized pigs had a significantly lower plasma Ca concentration before calcitonin administration. Calcitonin produced a hypocalcemic response in the pig similar to that observed in other species and with adequate dietary Ca lack of endogenous calcitonin (as a result of thyroidectomy) exerted little influence on plasma Ca concentration.

Natriuretic effect of calcitonin in man.

Abstract Porcine calcitonin was given to eight patients by continuous infusion for six to 39 days. Renal sodium and water excretion increased for 48 hours, and 0.5 to 1.6 kg of body weight was lost. A new steady state followed, with body weight below, sodium excretion the same as, and aldosterone secretion rate and plasma renin activity above, control levels. After the calcitonin infusion was stopped, there was sodium retention, and body weight returned to control values. Contamination or species difference as an explanation of these effects was unlikely because in short-term studies, porcine and synthetic human calcitonin had identical effects. The absence of a simultaneous increase in the excretion of cyclic adenosine-3′,5′-monophosphate suggests that the increase of sodium excretion was not due to a secondary increase of parathyroid-hormone secretion. Plasma calcitonin concentration achieved during continuous infusion suggests that calcitonin in physiologic amounts causes sufficient sodium and water lo...

Inhibitory effect of salmon and other calcitonins on calcium release from mouse bone in vitro.

Salmon calcitonin in a concentration of 0.8 ng/ml inhibited for 20 h cell-mediated release of 45Ca from cultured mouse calvaria. Porcine calcitonin in a concentration of 2500 ng/ml was much less effective. The response (percent inhibition) to salmon calcitonin was proportional to the logarithm of the dose over the range 0.012–0.20 ng/ml, and may provide a very sensitive in vitro bioassay for salmon calcitonin.

TREATMENT OF HYPERCALCÆMIA WITH CALCITONIN

Porcine calcitonin was given to patients with hypercalcæmia due to hyperparathyroidism and vitamin-D intoxication, and it reduced serum-calcium by as much as 3.5 mg. per 100 ml. The concentration of circulating exogenous calcitonin was measured by radio-immunoassay. Intravenous infusion (8 units per kg. per hour) yielded concentrations up to 22 ng. per ml., and intramuscular injection in gelatin concentrations up to 40 ng. per ml. Clearance of hormone from the circulation is rapid after intravenous infusion, and a short infusion seems to be a useful way of determining rapidly whether calcitonin will be effective in a given patient.

Comparison of Human, Porcine and Salmon Synthetic Calcitonins in Man and the Rat

Comparison of Human, Porcine and Salmon Synthetic Calcitonins in Man and the Rat

Direct measurement of in vivo secretion of pig thyrocalcitonin by radioimmunoassay.

The radioimmunoassay for porcine thyrocalcitonin (TC) was used to measure concentrations of the hormone in the thyroid venous effluent blood of young pigs. Thyroid venous blood was continuously and completely collected from the surgically isolated in situ thyroid gland. Control peripheral blood samples were obtained concurrently from a femoral artery. Alterations in the concentration of calcium in blood entering the thyroid gland were achieved by systemic infusions of solutions of CaCl2 or EDTA. Within minutes after exposure of the thyroid gland to hypercalcemia, the concentration of TC in thyroid venous effluent plasma increased from 10–20 to as much as 2000–3000 rg/ml. Hypocalcemia rapidly suppressed high concentrations of TC to undetectable levels. A proportional relationship between concentrations of calcium and TC in thyroid effluent blood was evident above 10 mg Ca/100 ml plasma. With the thyroid venous effluent blood entirely diverted from the systemic circulation, no hormone could be detected in a...