17 beta-Oxidation of estradiol and testosterone in the human testis.
The oxidation of 17 beta-estradiol in the human testis was studied in order to characterize a potentially important regulatory step in the action of estradiol in the human testis. 17 beta-Estradiol was shown to be converted to estrone, a weaker estrogen, in a reaction which was not inhibited by testosterone to any greater extent. When compared with the corresponding 17 beta-oxidation of testosterone, differences in coenzyme preferences, hydrogen ion sensitivity and inhibitions by estradiol and testosterone were observed, suggesting to a presence of different 17 beta-hydroxysteroid dehydrogenases in the human testis. Thus the human testis may counteract some of the deleterious effects of 17 beta-estradiol on androgen biosynthesis by metabolizing it to a weaker estrogen, in a reaction which probably is not inhibited by high testicular testosterone concentrations.
D015067:17-Hydroxysteroid Dehydrogenases / Q000378:metabolism; D000735:Androstenedione / Q000096:biosynthesis; D004958:Estradiol / Q000378:metabolism*; D004970:Estrone / Q000096:biosynthesis; D006801:Humans; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D009249:NADP / Q000378:metabolism; D010084:Oxidation-Reduction; D013737:Testis / Q000378:metabolism*; D013739:Testosterone / Q000378:metabolism*
D004970:Estrone; D013739:Testosterone; D000735:Androstenedione; D004958:Estradiol; D009249:NADP; D015067:17-Hydroxysteroid Dehydrogenases