Comparison of the Regulation of Calcitonin in Serum of Old and Young Buffalo Rats

Abstract

Studies were carried out to characterize the secretion and the effects of calcitonin in the Buffalo rat. Mean basal concentrations of calcitonin and parathyroid hormone were significantly increased in serum of rats older than 6 months of age as compared with rats between 2 and 3 months of age. The mean concentration of calcium in serum was independent of age. In both age groups, serum calcitonin was increased by administration of calcium (1 mmol/kg body wt) or isoproterenol (100 microgram/kg body wt), was diminished by beta-adrenergic blockade with DL-propranolol (1 mg/kg body wt) and was not altered by either pentagastrin or glucagon (200 and 100 microgram/kg body wt respectively). The average weight of the thyroid glands was significantly greater in the old than in the young animals but the mean concentration of calcitonin in the thyroids was the same. Thyroparathyroidectomy produced a transient increase followed by a fall in mean serum calcium in the old rats. In contrast, a progressive decline in the mean concentration of calcium in serum was observed after thyroparathyroidectomy in the young rats. Treatment of old animals with reserpine (2.5 mg/kg body wt) markedly depleted noradrenaline in the thyroid, lowered calcitonin in serum and converted the pattern of response of serum calcium to thyroparathyroidectomy to that observed in young animals. The results provide evidence that hypercalcitonaemia occurs in aged Buffalo rats, as does hyperparathyroidism, and that the concentrations of calcitonin in blood are modulated by beta-adrenergic affectors. Glucagon and pentagastrin exhibit little if any effects on calcitonin secretion in this strain of rat regardless of age.

Age, Strain and Species Differences in Circulating Parathyroid Hormone

“…We also made the novel observation that in male F344 rats circulating PTH increases with advancing age. In a less rigorous study in terms of aging, Queener et al (1980) have also reported that the serum PTH of "young Buffalo rats" between 2 and 3 months of age was lower than that of "old rats" 6 months of age or older. The age-related increase in circulating PTH observed in our study was not associated with a decrease in serum calcium or alterations in serum proteins (not reported).…”

Effect of age on renal responsiveness to parathyroid hormone and calcitonin in rats

“…In rats, serum concentrations of both immunoreactive PTH and calcitonin (Queener, Bell, Larson et al 1980;Armbrecht, Forte & Halloran, 1984 ) increase with age, but serum l,25-(OH)2D declines with age (Gray & Gambert, 1982;Armbrecht et al 1984 ). In man, serum 1,25-(OH)2D also declines with age (Gallagher, Riggs, Eisman et al 1979) despite a rise in serum PTH (Gallagher, Riggs, Jerpbak & Arnaud, 1980).…”

Lack of influence of isoproterenol, propranolol, and dopamine on immunoreactive parathyroid hormone and calcitonin in normal man

“…Similarly, in the rat, serum immunoreactive CT is increased by isoproterenol and decreased by propranolol [10]. On the other hand, changes in serum PTH and plasma CT, in response to alteration of serum calcium produced by calcium and EDTA, were not altered following chemical sympathectomy by 6-hydroxydopamine in that species [11].…”