Synthesis of 17,20α- and 17,20β-dihydroxy-4-pregnen-3-ones, 11-ketotestosterone and their conjugates by gills of teleost fish
Goldfish, carp and trout gills were incubated with 3H-17-hydroxyprogesterone (17P). With goldfish gills, the metabolites were 17,20α-dihydroxy-4-pregnen-3-one (17,20αP; 82%), 17,20β-dihydroxy-4-pregnen-3-one (17,20βP; 8%), 11-ketotestosterone (KT) glucuronide (5.4%) and 17,20αP glucuronide (0.2%). Sulfates were not detected. Carp gills converted 17P into 17,20αP (11.2%), 17,20βP (9.6%), KT (8.4%), glucuronides of 17,20αP (1.3%) and 17,20βP (1.6%) and sulfates of 17,20αP (5.1%) and 17,20βP (7.2%). 17,20βP (38% free, 1.8% glucuronide and 21.1% sulfate) was the sole metabolite of 3H-17P in trout gill incubations. In the presence of high (10; µg ml-1) substrate concentration, cyprinid gills gave predominantly free 17,20αP, while trout gills yielded only free 17,20βP. Production of 17,20βP, predominantly as its sulfate, from endogenous precursors was demonstrated in trout gills but was not stimulated by trout primary extract. Our results demonstrate for the first time the steroidogenic potential of teleost gills and suggest that they may play a role in secretion of pheromones in some species.