Effects of C19 steroids on adrenal steroidogenic enzyme activities and their mRNA levels in guinea-pig fasciculata-glomerulosa cells in primary culture.

The present study examined the effects of steroids on steroidogenic enzyme activity in adrenal glands. Guinea-pig fasciculata-glomerulosa (FG) cells maintained in primary culture were exposed to steroids for 48 h. Although the treatment with androstenedione alone had no effect on 3 beta-hydroxysteroid dehydrogenase 4-ene-5-ene-isomerase (3 beta-HSD), 17-hydroxylase and 17,20-lyase activities, there was inhibition of 11-hydroxylase and 21-hydroxylase activities. When FG cells were exposed to 10 nmol ACTH/l for the last 24 h of incubation, ACTH alone had no effect on steroidogenic enzymes but, while combined with androstenedione, it further decreased 21-hydroxylase activity and stimulated 17-hydroxylase and 17,20-lyase activities. Cortisol, corticosterone, oestradiol and 11 beta-hydroxy androstenedione had no effect on steroidogenic enzyme activities while the inhibitory effect on 21-hydroxylase activity was only observed with androstenedione, testosterone and dihydrotestosterone. Addition of hydroxyflutamide, a pure antiandrogen, did not block the inhibitory effect of androstenedione on 21-hydroxylase and 11-hydroxylase activities. The reduction in oxygen tension from 19 to 2% which was aimed at examining the oxygen-mediated effects on steroidogenic enzymes, revealed that the reduction in 21-hydroxylase activity induced by androstenedione could not be prevented by low oxygen tension. An interaction of C19 steroids at the level of the enzymes is also suggested by our finding that androstenedione had no effect on basal and ACTH-stimulated steady-state 11-hydroxylase, 17-hydroxylase, 17,20-lyase and 21-hydroxylase mRNA levels.(ABSTRACT TRUNCATED AT 400 WORDS)