In vitro bioconversion of [14C]androstenedione by testes of the Siamese fighting fish Betta splendens Regan (Anabantoidei, Belontiidae).

Minced testes of the Siamese fighting fish Betta splendens were incubated with [14C]androstenedione at 27 degrees C for 15, 30, 60, and 120 min. The metabolic products were characterized by paper and thin-layer chromatography, derivative formation, and eventually by crystallization to constant specific activity. After 2 hr of incubation 80.5% of total radioactivity was converted to 11-oxygenated androgens. 11-Ketotestosterone was the main metabolite (56.2%). Our data suggest the existence of two biosynthetic pathways for the formation of 11-ketotestosterone from androstenedione. The sequence androstenedione----testosterone----11 beta-hydroxytestosterone----11-ketotestosterone predominates. To a lesser extent 11 beta-hydroxylation takes place as the first step--followed by formation of 11 beta-hydroxytestosterone and its subsequent oxidation to 11-ketotestosterone.