Pubertal development of male African catfish, Clarias gariepinus. In vitro steroidogenesis by testis and interrenal tissue and plasma levels of sexual steroids

In fish, sex steroids initiate and/or accelerate the maturation of the brain-pituitary-gonad axis. In order to obtain information on the steroid milieu during the pubertal development of male African catfish, we have monitored the conversion of [H-3]-pregnenolone and [H-3]-androstenedione by testis and [H-3]-pregnenolone by interrenal tissue fragments in vitro. Pubertal development occurs between two and six months of age. Testicular development proceeds through four main stages that are characterised histologically by the presence of spermatogonia (stage I), spermatogonia and spermatocytes (stage II), spermatogonia, spermatocytes and spermatids (stage III), and all germ cells including spermatozoa (stage IV). 11 beta-Hydroxyandrostenedione and cortisol were the main products of testes and interrenal tissue, respectively, in all stages of the pubertal development; a change in the steroidogenic pattern was not observed during this period. The interrenal tissue displayed no significant conversion of [H-3]-pregnenolone to Ii-oxygenated androgens. Blood plasma was analyzed for the presence of five androgens; testosterone, 11 beta-hydroxytestosterone, 11 beta-hydroxyandrostenedione, androstenetrione, and 11-ketotestosterone. 11-Ketotestosterone was the quantitatively dominating androgen in the circulation at all stages of development, which was more pronounced in stages III and IV. The obvious differences between the in vitro and in vivo results, namely 11 beta-hydroxyandrostenedione being the main testicular product vs. 11-ketotestosterone dominating in the blood,may indicate that 11 beta-hydroxyandrostenedione is converted to 11-ketotestosterone at extratesticular sites.