20α-hydroxysteroid dehydrogenase activity in the rat corpus luteum; A quantitative cytochemical study

摘要: A quantitative cytochemical method for the demonstration of 20 alpha-hydroxysteroid dehydrogenase activity (20 alpha-HSD) in regressing corpora lutea adult rat ovary is described. The employs unfixed tissue sections and relies upon oxidation alpha-hydroxy-4-pregnen-3-one alpha-OH-P) with nitro blue tetrazolium as hydrogen acceptor. enzyme was dependent NADP+ its inactive when beta-hydroxy-4-pregnen-3-one beta-OH-P) used a substrate. apparent Km values alpha-OH-P were 3 x 10(-4) M 2.5 10(-5) respectively. Inhibition alpha-HSD by steroids demonstrable at pH 8. Androstenedione far most potent inhibitor, followed progesterone (the product activity) 17 alpha-hydroxyprogesterone, Compound S beta-OH-P. At 6.8, more favourable to leads reaction, only alpha-hydroxyprogesterone inhibitory. Testosterone without effect either pH.