EXTRAGONADAL PRODUCTION OF 17,20-DIHYDROXY-4-PREGNEN-3-ONES IN-VITRO IN CYPRINID FISH

Muscle, heart, eye, testis, blood, and sperm of trout and goldfish hav e been examined for the presence of 20-hydroxysteroid dehydrogenase by incubation with [H-3]17-hydroxyprogesterone in the presence of 0, 0.1 , 1, or 10 mu g/ml of unlabeled substrate. In trout, 17-hydroxyprogest erone was metabolized only by sperm and testis, with 17,20 beta-dihydr oxy-4-pregnen-3-one (17,20 beta P) as the major product and traces (< 2%) of 17,20 alpha-dihydroxy-4-pregnen-3-one (17,20 alpha P). In goldf ish, maximum conversion of 17-hydroxyprogesterone to 17,20 alpha P was over 30% per 100 mg tissue in eyeball, heart, and testis, 12% per 20 mu l blood, and 18% per 20 mu l sperm, but less than 5% per 100 mg mus cle. 17,20 alpha P was the only metabolite of 17-hydroxyprogesterone i n all incubations of nongonadal tissue in goldfish. Within the cyprini d eye, there was no significant activity in the lens, the fluids, or t he retina. The possible relationship between the teleost 20 alpha- and 20 beta-hydroxysteroid dehydrogenases, the mammalian 20-hydroxysteroi d dehydrogenases, and members of the aldo-keto reductase and short-cha in dehydrogenase superfamilies is discussed. (C) 1996 Academic Press, Inc.