3β-hydroxysteroid dehydrogenase/Δ
5−Δ
4isomerase (3β-HSD) activity was measured in primary dissociated cell cultures prepared from telencephalons of developing zebra finches. 3β-HSD activity was confirmed after cultures were incubated with [7-
3H]pregneno- lone (Preg) or (1,2,6,7-
3H-) dehydroepiandrosterone (DHEA) and
3H-progesterone (Prog) and
3H-androstenedione (AE) were detected in the medium. Product identity was confirmed by recrystallizations and by HPLC analysis. When DHEA was used as substrate,
3H-estradiol and
3H-estrone were also detected in the culture medium, presumably derived from the aromatization of
3H-AE or
3H-T produced from
3H-DHEA. To test this idea, cultures were incubated with
3H-DHEA together with radioinert AE or with fadrozole HCl, a potent and specific aromatase inhibitor. In the presence of radioinert AE,
3H-AE increased but metabolites of
3H-AE decreased in the media; in the presence of fadrozole,
3H-estrogens decreased but
3H-AE and its androgenic metabolite
3H-5β-androstanedione increased. These data demonstrate 3β-HSD activity in the songbird brain. The presence of Prog and estradiol in these cultures suggest that Preg and DHEA can potentially serve as substrates for the ultimate formation of active sex steroids in the songbird telencephalon.
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