Failure to demonstrate stimulatory effect of prolactin on vitamin D metabolism in vitamin-D-deficient rats.
The effect of administration of bovine prolactin in vivo on renal 1 alpha-hydroxylase (1 alpha-OHase) activity was investigated using thyroparathyroidectomized and sham-operated vitamin-D-deficient male rats. A high dose (1.5 IU/hr) and a low dose (0.3 IU/hr) of bovine prolactin was constantly infused into the cannulated femoral vein for 6 hr or 30 hr. The accumulation of 1 alpha, 25-hydroxyvitamin D3 [1 alpha, 25-(OH)2-D3] in plasma produced from 25-hydroxy-vitamin D3 (25-OH-D3) was calculated from the 6-hr conversion of intravenously injected [3H]-25-OH-D3 to [3H]-1 alpha, 25-(OH)2-D3. Both high dose and low dose of prolactin administration caused no significant stimulatory effect on 1 alpha-OHase activity in TPTX animals. Also, in sham-operated rats the prolactin treatment produced no significant change in the 1 alpha-OHase activity. Plasma calcium concentrations showed a tendency to increase slightly. These results suggest that prolactin has no direct stimulatory role on renal 1 alpha-OHase activity in rats. Its effect on calcium metabolism may be mediated by a different mechanism(s).
D000818:Animals; D002118:Calcium / Q000097:blood; D004305:Dose-Response Relationship, Drug; D007668:Kidney / Q000201:enzymology; D008297:Male; D006899:Mixed Function Oxygenases / Q000378:metabolism; D011388:Prolactin / Q000494:pharmacology*; D051381:Rats; D014807:Vitamin D / Q000378:metabolism*; D014808:Vitamin D Deficiency / Q000097:blood / Q000378:metabolism*
D014807:Vitamin D; D011388:Prolactin; D006899:Mixed Function Oxygenases; D002118:Calcium