Abstract
Summary
Adrenal 5α-reductase activity was measured in female rats 0, 2, 5, and 6 days after hypophysectomy. Enzyme activity increased progressively exhibiting a 35-fold elevation at 6 days. The effects of high (250 μg/100 g of body wt), intermediate (25 μg/ 100 g of body wt), and low (2.5 μg/100 g of body wt) daily doses of bovine prolactin and bovine growth hormone were compared at 2 and 5 days posthypophysectomy. At 2 days, enzyme activity was partially inhibited by the high and intermediate doses of prolactin and not affected by growth hormone. At 5 days all doses of prolactin were inhibitory, whereas enzyme activity was suppressed only by the high dose of growth hormone. With a given dose of hormone, the amount of suppression of enzyme activity is greater at 5 days than at 2 days posthypophysectomy. In 5-day hypophysectomized rats the inhibitory effects of prolactin and growth hormone were additive. It is concluded that: (i) hormonal sensitivity and responsiveness of the adrenal reductase pathway increases with duration of pituitary ablation; (ii) the reductase pathway is more sensitive to the effects of prolactin than growth hormone; and (iii) the effects of growth hormone and prolactin on reductase activity are mediated via different mechanisms, as suggested by the additive effects of individual hormones.
Get full access to this article
View all access options for this article.