Role of adrenal 5alpha-reductase activity in determining the responsiveness of hypophysectomized rats to ACTH.
Studies were conducted to examine the contribution of adrenal 5alpha-reductase to the phenomenon of diminished adrenal "responsiveness" to ACTH after hypophysectomy in rats. Rats hypophysectomized for 1 week secreted small amounts of corticosterone (B), 5alpha-dihydrocorticosterone (DHB) and 3beta,5alpha-tetrahydrocorticosterone (R) acutely after ACTH. Adrenal reductase activity in vitro at that time was high. After replacement with ACTH for 24 h, B,DBH, and R secretion increased slightly. Reductase activity remained high. Treatment with ACTH for 2 days further stimulated secretion of DHB  and R but not B. Reductase activity was unaffected. Enzyme activity declined at 3 days concomitant with a proportionately greater increase in B than DHB and R secretion. Only after 7 days of ACTH did B secretion exceed DHB and R output. At that time, reductase activity was still lower. The results establish the functional significance of 5alpha-reductase activity as a regulatory site for the action of ACTH in determining the composition of adrenocortical secretory products in hypophysectomized rats.
D000311:Adrenal Glands / Q000201:enzymology* / Q000378:metabolism; D000324:Adrenocorticotropic Hormone / Q000494:pharmacology*; D000818:Animals; D003345:Corticosterone / Q000031:analogs & derivatives / Q000378:metabolism; D005260:Female; D007016:Hypophysectomy; D010088:Oxidoreductases / Q000502:physiology*; D051381:Rats; D013268:Stimulation, Chemical; D013997:Time Factors
D000324:Adrenocorticotropic Hormone; D010088:Oxidoreductases; D003345:Corticosterone