Co-induction of 17α-hydroxylase and c-17,20-lyase activities in primary cultures of bovine adrenocortical cells in response to ACTH treatment

Abstract

Bovine adrenocortical cells in primary culture were used to examine the trophic effect of ACTH on the induction of the 17α-hydroxylase and C-17,20-lyase activities. The addition of exogenous pregnenolone to bovine adrenal microsomes showed the appearance of 17α-hydroxypregnenolone before the formation of dehydroepiandrosterone. The same sequence of activities was evident in postmitochondrial supernate from bovine adrenocortical cells cultured 36 h in the presence of 1 μM ACTH but not in postmitochondrial supernate from control cells. In another study, bovine adrenocortical cells were cultured for 36 h after which 30μM 17α-hydroxypregnenolone was added to the medium and the incubation continued 1 h; there was a 4-fold increase in androgen content in the media from ACTH-treated cells over controls. Measurement of the 17α-hydroxylase and C-17,20-lyase reactions in postmitochondrial supernate from cells cultured 0–72 h in the presence of ACTH or 1 mM dibutyryl cAMP showed concomitant increases in the two activities and both activities were inhibited by the same compounds known to inhibit 17α-hydroxylase activity. These observations support the concept of the co-induction of 17α-hydroxylase and C-17,20-lyase activities in response to ACTH; results in keeping with previous studies indicating that the two activities are catalyzed by a single gene product, the polypeptide chain P-450 17a.