Vitamin A stimulation of parathyroid hormone: interactions with calcium, hydrocortisone, and vitamin E in bovine parathyroid tissues and effects of vitamin A in man.
The effect of vitamin A, a membrane surface-active agent, on parathyroid hormone secretion was studied in vitro, using bovine parathyroid tissue, and in vivo in man. Parathyroid tissues were incubated with vitamin A (retinol), retinoic acid, and calcium, and with hydrocortisone and vitamin E, agents that antagonize the membrane effects of vitamin A. The stimulation of parathyroid hormone release by vitamin A, 10(-6) to 10(-9) mol/1 in vitro, was dose and time dependent. Retinoic acid did not stimulate secretion. High calcium concentration, hydrocortisone, 10(-5) mol/1 and 10(-6) mol/1, and vitamin E, 10(-5) mol/1, antagonized vitamin A-induced parathyroid hormone secretion. Vitamin A increased the lysosomal cathepsin D activity of parathyroid tissues. In human studies, eleven healthy men received two intramuscular injections of vitamin A palmitate, 25 000 units each, within 24 h. In every subject, serum parathyroid hormone increased after vitamin A administration. Our studies indicate that: (1) vitamin A stimulates parathyroid hormone secretion in vitro, possibly through modification of the cell or secretion granule membrane, or through stimulation of lysosomal proteolytic activity, and (2) vitamin A increases serum parathyroid hormone in vivo, and this effect may be important in clinical states of vitamin A excess.
D000328:Adult; D000818:Animals; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology*; D002417:Cattle; D006801:Humans; D006854:Hydrocortisone / Q000494:pharmacology*; D008247:Lysosomes / Q000187:drug effects / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D010280:Parathyroid Glands / Q000187:drug effects / Q000378:metabolism*; D010281:Parathyroid Hormone / Q000097:blood / Q000378:metabolism*; D011863:Radioimmunoassay; D014801:Vitamin A / Q000494:pharmacology*; D014810:Vitamin E / Q000494:pharmacology*
D010281:Parathyroid Hormone; D014801:Vitamin A; D014810:Vitamin E; D002118:Calcium; D006854:Hydrocortisone