[Effect of 1,25-dihydroxycholecalciferol and 24,25-dihydroxycholecalciferol on thyroid calcitonin content in the suckling or weanling rat].
We have examined the effects of vitamin D3 metabolites on plasma calcium, plasma calcitonin (CT) and thyroidal CT contents in Rats before and after weaning. A daily injection of 1,25-dihydroxycholecalciferol [1,25-(OH)2D3; approximately 25 pmoles/Rat/day during 4 days] induced a marked rise in plasma calcium (16.1 +/- 0.2 vs. 11.3 +/- 0.3 mg/dl in controls) and a great decrease in thyroidal CT content (-70% of control values) in 13-day-old suckling baby Rats, while no change occurred in response to 24,25-dihydroxycholecalciferol (24,25-(OH)2D3) administration. A negative correlation between plasma calcium level and thyroidal CT stores was found in suckling and in weaning Rats treated with different doses of 1,25-(OH)2D3. The significant difference between the slopes of the two regression lines demonstrated a greater mobilization of the CT stores in weaning than in suckling Rats in response to a given hypercalcemia. Our results could suggest that 24,25-(OH)2D3 at the dose used, does not regulate CT secretion while 1,25-(OH)2D3 has probably an indirect effect on CT release, but in vitro experiments will be performed to confirm this hypothesis.
D015650:24,25-Dihydroxyvitamin D 3; D000818:Animals; D002116:Calcitonin / Q000378:metabolism*; D002117:Calcitriol / Q000494:pharmacology*; D004100:Dihydroxycholecalciferols / Q000494:pharmacology*; D005260:Female; D006801:Humans; D007700:Kinetics; D007774:Lactation; D011247:Pregnancy; D051381:Rats; D011919:Rats, Inbred Strains; D013961:Thyroid Gland / Q000187:drug effects / Q000254:growth & development* / Q000378:metabolism; D014886:Weaning
D004100:Dihydroxycholecalciferols; D015650:24,25-Dihydroxyvitamin D 3; D002116:Calcitonin; D002117:Calcitriol
Effets du 1.25-dihydroxycholécalciférol et du 24.25-dihydroxycholécalciférol sur la teneur thyroïdienne en calcitonine chez le Raton allaité ou sevré.