In vitro biosynthesis of novel 5beta-reduced steroids by the testis of the round goby, Neogobius melanostomus.

Previous studies indicate that, in the round goby Neogobius melanostomus, the reproductively mature male releases a pheromone that attracts ripe females. Furthermore, studies suggest that the pheromone may be a steroid (more specifically a 5beta-reduced androgen) produced by specialized glandular tissue in the testes. In the present study, it is shown that the testis of the male round goby contains such specialized glandular tissue. In vitro, the testes convert [3H]androstenedione into 3alpha-hydroxy-5beta-androstane-11,17-dione (i.e., 11-oxo-etiocholanolone, 11-oxo-ETIO); 11-oxo-ETIO sulfate (11-oxo-ETIO-s); 11-oxo-testosterone (i.e., 11-ketotestosterone), 3alpha-hydroxy-5beta-androstan-17-one (etiocholanolone, ETIO); 11beta-hydroxy-androstenedione; ETIO sulfate and testosterone. Glucuronidated steroids were not identified. Neither 11-oxo-ETIO nor 11-oxo-ETIO-s has previously been identified in teleost gonads. Both these steroids are formed in the round goby testis even when [3H]17-hydroxyprogesterone is used as a precursor. The fact that, for both steroids, the carbon A ring has a 5beta-configuration (already linked with olfactory sensitivity and behavior induction in two other species of gobies) makes them likely candidate pheromones in the round goby. However, their in vivo production and pheromonal activity remain to be proved.