Abstract
1. 1. The stereoselective hydroxylation of testosterone by microsomal cytochrome P-450 and the changes in level of components participated in the microsomal electron transport system were observed in the microsomes induced unique P-450 isozymes. 2. 2. Flavone- and hesperetin-inducible P-450 catalyzed the hydroxylation of testosterone more effectively than other chemicals-inducible ones. 3. 3. The P-450 in all the microsomal preparations tested most rapidly oxidized testosterone to 6β-monohydroxy form. 4. 4. Particularly, MC- and BNF-inducible P-450 showed high stereoselectivity on C6-position of testosterone, and PB-, flavone- and hesperetin-inducible one showed that on C2-position of this compound, respectively. 5. 5. This specificity of two flavonoid-inducible P-450 for the formation of 2α- and 2β-epimer ofmonohydroxytestosterone was opposite to each other. 6. 6. The content of P-450 and the activity of NADPH-cytochrome P-450 reductase were high in PB-, MC- and BNF-microsomes, whereas NADH-cytochrome b 5 reductase activity was high in two flavonoidmicrosomes and the content of cytochrome b 5 was not changed except the PB-treated rats. 7. 7. It is suggested that the increasing activities of testosterone hydroxylases in flavonoid-microsomes seems to be closely related to NADH-cytochrome b 5 reductase.
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