Regulation of the receptor-mediated cyclic AMP response of kidney to parathyroid hormone in the vitamin D-deficient rat

✍ Scribed by Forte, Leonard R. ;Carnes, David L. ;Nickols, G. Allen ;Anast, Constantine S.

• Publisher: Wiley (John Wiley & Sons)
• Year: 1978
• Tongue: English
• Weight: 560 KB
• Volume: 9
• Category: Article
• ISSN: 0091-7419
• DOI: 10.1002/jss.400090204

✦ Synopsis

Rats fed a diet deficient in vitamin D were found t o exhibit a refractory cyclic AMP response of kidney slices to parathyroid hormone and a marked decrease in membrane parathyroid hormone-dependent adenylate cyclase activity. Both the characteristic calcium deficiency (hypocalcemia) and secondary elevation of circulating parathyroid hormone appeared before the first noticeable decrease in hormone-dependent enzyme activity. After repletion of D-deficient rats with vitamin D 2 , we found that serum calcium and parathyroid hormone were both restored to normal levels before t h e depressed enzyme response t o the hormone was reversed. Moreover, infusion of parathyroid hormone into vitamin D-replete rats led t o a marked reduction in parathyroid hormonedependent adenylate cyclase activity, which was partly restored to control level 3 hours after discontinuing the hormone infusion. Taken as a whole, this study suggests that the elevated endogenous parathyroid hormone in the vitamin D-deficient rat is involved in the "down-regulation'' of renal cyclic AMP responsiveness to the hormone. However, these experiments do not rule out the possibility that calcium deficiency and/or vitamin D per se participate in the regulation of the renal cyclic AMP response t o parathyroid hormone.