title: Calcitonin secretion during postnatal development in the rat: beta-adrenergic agents and vitamin D3 metabolites.
abstract: The possible contribution of catecholamines and vitamin D3 metabolites to the high plasma calcitonin (CT) levels in suckling baby rats is unknown. So, in vivo and in vitro (using a perifusion system) effects of beta-adrenergic agents and vitamin D3 metabolites on CT release were studied in the rat during the postnatal development. In 13-day-old rats, the increase in plasma CT levels induced by isoproterenol injection (0.1 micrograms/kg b.w.) was inhibited by a previous administration of propranolol. A significant decrease in plasma CT levels was observed after propranolol injection in baby rats (0.68 +/- 0.05 ng/ml vs. 0.93 +/- 0.01 ng/ml). A daily injection of 1,25-dihydroxycholecalciferol (1,25-(OH)2D3; 25 pmoles/rat/day during 4 days) induced a marked rise in plasma calcium (16.1 +/- 0.2 mg/dl), and a great decrease in thyroidal CT contents (approximately 70% of control values) in 13-day-old rats while no change was noted with 24,25-dihydroxycholecalciferol (24,25-(OH)2D3). A negative correlation between plasma calcium and thyroidal CT stores was found in suckling and in weaning rats treated with different doses of 1,25-(OH)2D3, suggesting an indirect effect of 1,25-(OH)2D3 on CT secretion. The mobilization of the thyroidal CT content was greater in weaning than in suckling rats in response to a given hypercalcemia. In vitro, 5 X 10(-5) M isoproterenol induced a rapid increase in CT secretion rate while 1,25-(OH)2D3 inhibited the rise in CT release induced by 3.0 mM calcium.(ABSTRACT TRUNCATED AT 250 WORDS)
mesh_terms: D015650:24,25-Dihydroxyvitamin D 3; D000318:Adrenergic beta-Agonists / Q000494:pharmacology*; D000818:Animals; D002116:Calcitonin / Q000378:metabolism*; D002117:Calcitriol / Q000494:pharmacology; D004100:Dihydroxycholecalciferols / Q000494:pharmacology*; D007545:Isoproterenol / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D013961:Thyroid Gland / Q000254:growth & development / Q000378:metabolism*
chemical_list: D000318:Adrenergic beta-Agonists; D004100:Dihydroxycholecalciferols; D015650:24,25-Dihydroxyvitamin D 3; D002116:Calcitonin; D011433:Propranolol; D002117:Calcitriol; D007545:Isoproterenol