Salmon calcitonin-induced stimulation of 1 alpha,25-dihydroxycholecalciferol synthesis in rats involving a mechanism independent of adenosine 3':5'-cyclic monophosphate.
The effect of natural salmon calcitonin on accumulation in plasma of 1 alpha,25-dihydroxy-[3H]cholecalciferol from 25-hydroxy[3H]cholecalciferol in vivo was investigated in vitamin D-deficient thyroparathyroidectomized rats into which graded doses of the hormone were continuously infused by use of a balance study system. A dose-dependent increase in plasma concentrations of 1 alpha,25-dihydroxy[3H]cholecalciferol was observed with calcitonin infusion for 6--30h at a rate greater than 20 M.R.C. m-units/h. Infusion of parathyrin or cyclic AMP produced a similar stimulation [Horiuchi, Suda, Takahashi, Shimazawa & Ogata (1977) Endocrinoly 101, 969--974], but the maximal effect of calcitonin was additive to that of either parathyrin or cyclic AMP. Furthermore concurrent infusion of theophylline (0.5 mumol/h) did not potentiate the effect of submaximal doses (3 and 20 M.R.C. m-units/h) of calcitonin. Plasma concentrations of calcium showed a decrease with calcitonin infusion for 30h, but those of Pi remained unchanged. These results strongly suggest that the rat kidney is endowed with a calcitonin-sensitive 1 alpha-hydroxylase system that is separate from the parathyrin/cyclic AMP system and is independent of changes in plasma Pi.
D000818:Animals; D002116:Calcitonin / Q000494:pharmacology*; D002118:Calcium / Q000097:blood; D000242:Cyclic AMP / Q000494:pharmacology; D004100:Dihydroxycholecalciferols / Q000096:biosynthesis* / Q000097:blood; D004305:Dose-Response Relationship, Drug; D006887:Hydroxycholecalciferols / Q000096:biosynthesis*; D008297:Male; D010280:Parathyroid Glands / Q000502:physiology; D010281:Parathyroid Hormone / Q000494:pharmacology; D010710:Phosphates / Q000097:blood; D051381:Rats; D013268:Stimulation, Chemical; D013806:Theophylline / Q000494:pharmacology; D013965:Thyroidectomy; D014808:Vitamin D Deficiency / Q000378:metabolism
D004100:Dihydroxycholecalciferols; D006887:Hydroxycholecalciferols; D010281:Parathyroid Hormone; D010710:Phosphates; D002116:Calcitonin; D013806:Theophylline; D000242:Cyclic AMP; D002118:Calcium