Effect of 4-cholesten-3-one on 3 beta-hydroxysteroid dehydrogenase activity in rat adrenals

4-Cholesten-3-one inhibited the activity of 3 beta-hydroxy-delta 5-steroid dehydrogenase (EC 1.1.1.145) in the microsomal cytoplasmic supernatant of rat adrenal homogenate when using 3 beta-hydroxy-5-androsten-17-one (DHA) as the substrate. The inhibition was sex dependent: in male adrenals it reached more than 51%, whereas in female glands it was not significant. The side-chain cleavage of [26-14C]-cholestenone in the mitochondrial rat adrenal preparation measured as labelled isocaproic acid was extremely low in comparison with [26-14C]-cholesterol.