[Steroidogenesis in isolated adrenal cells of rat. -Effects of cyanoketone on pregnenolone and corticosterone production- (author's transl)].

In order to study the effect of cyanoketone on steroidogenesis of rat adrenal, the assay technique for corticosteroids released into the incubated media of the rat adrenal cells treated with collagenase was basically investigated. Corticosterone was measured by fluorometric method and pregnenolone by radioimmunoassay. Reliability of radioimmunoassay was satisfactory. About 400,000 cells were obtained from one adrenal gland of male or female rats and sex-dependent difference in pregnenolone and corticosterone production in response to ACTH was not found. Net corticosterone production by isolated adrenal cells was related to the log of the concentration of ACTH by a sigmoid curve over the range 1 to 1000 muU/ml. The half-maximum response was observed at an ACTH concentration of 10 muU/ml, and maximum corticosterone production responding to ACTH (100-1000 muU/ml) was about 5 mug/adrenal/120 min. When cell suspensions were incubated with 1000 muU/ml of ACTH, the conversion from pregnenolone to corticosterone was inhibited 50% by cyanoketone at a concentration of 2 times 10(-8) M. The conversion was completely inhibited at a concentration of more than 10(-7) M. Cyanoketone up to a concentration of 10(-5) M seemed to have no inhibitory effect on cholesterol side-chain cleavage. In the absence of ACTH significant amount of pregnenolone was formed (about 60 ng/adrenal) by isolated adrenal cells obtained from normal adult female rats during incubation with 10(-7) M of cyanoketone for 60 min. To eliminate the possibility of the effect of endogenous ACTH which might be present in incubation medium, cell suspensions were obtained from hypophysectomized female rats. Incubations were carried out in the same condition as mentioned above and significant amount of pregnenolone was formed by cell suspension, which was about 35 ng/adrenal.