Testosterone metabolism in rooster comb

Abstract

After testosterone was incubated with the cell-free homogenates of rooster comb in air in the presence of NADPH, 5β-androstane-3β,17β-diol was identified as the major metabolite and 5α-dihydrotestosterone, 5β-dihydrotestosterone, 5α-an-drostane-3α, 17β-diol and 5β-androstane-3α,17β-diol were also obtained. Among the subcellular fractions, 5α-reductase activity was mostly detected in the microsomal fraction (10000–105000 × g), while 5β-reductase activity was exclusively found in the cytosol fraction (supernatant fluid at 264000 × g). 3α-Hydroxysteroid dehydrogenase (EC 1.1.1.50) which prefered 5α-dihydrotestosterone as the substrate was localized in the cytosol and microsomal fractions, but the dehydrogenase which prefered 5β-dihydrotestosterone was found in the microsomal and mitochondrial (800–6000 × g) fractions. 3β-Hydroxysteroid dehydrogenase (EC 1.1.1.51) which reduced 5β-dihydrotestosterone but not its 5α-epimer was found mainly in the cytosol fraction. The 3α- and 3β-hydroxysteroid dehydrogenases in the cytosol and microsomal fractions of the comb utilized specifically 4-pro-S-H of NADPH for reduction of the oxo group of 5α- and 5β-dihydrotestosterones. With aging, 5α-reductase activity showed a decrease, whereas 5β-reductase remained unchanged. Among the metabolites, the 5α-hydrogenated steroids showed significant androgenic activities, but the 5β-hydrogenated steroids showed no comparable activities upon cockerel comb. Androgenic activity of 5α-dihydrotestosterone upon the comb was significantly reduced by simultaneous administration of 5β-dihydrotestosterone.