3-BETA-HYDROXYSTEROID DEHYDROGENASE ISOMERASE AND AROMATASE-ACTIVITY IN PRIMARY CULTURES OF DEVELOPING ZEBRA-FINCH TELENCEPHALON - DEHYDROEPIANDROSTERONE AS SUBSTRATE FOR SYNTHESIS OF ANDROSTENEDIONE AND ESTROGENS/

3 beta-hydroxysteroid dehydrogenase/Delta(5)-Delta(4) isomerase (3 bet a-HSD) activity was measured in primary dissociated cell cultures prep ared from telencephalons of developing zebra finches. 3 beta-HSD activ ity was confirmed after cultures were incubated with [7-H-3]pregnenolo ne (Preg) or (1,2,6,7-H-3-) dehydroepiandrosterone (DHEA) and H-3-prog esterone (Frog) and H-3-androstenedione (AE) were detected in the medi um. Product identity was confirmed by recrystallizations and by HPLC a nalysis. When DHEA was used as substrate, H-3-estradiol and H-3-estron e were also detected in the culture medium, presumably derived from th e aromatization of H-3-AE or H-3-T produced from H-3-DHEA. To test thi s idea, cultures were incubated with H-3-DHEA together with radioinert AE or with fadrozole HCl, a potent and specific aromatase inhibitor. In the presence of radioinert AE, H-3-AE increased but metabolites of H-3-AE decreased in the media; in the presence of fadrozole, H-3-estro gens decreased but H-3-AE and its androgenic metabolite H-3-5 beta-and rostanedione increased. These data demonstrate (3) beta-HSD activity i n the songbird brain. The presence of Frog and estradiol in these cult ures suggest that Preg and DHEA can potentially serve as substrates fo r the ultimate formation of active sex steroids in the songbird telenc ephalon. (C) 1996 Academic Press, Inc.