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

Abstract

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 [ 3 H]-pregnenolone and [ 3 H]-androstenedione by testis and [ 3 H]-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 -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 [ 3 H]-pregnenolone to 11-oxygenated androgens.Blood plasma was analyzed for the presence of five androgens; testosterone, 11 ,-hydroxytestosterone, 11 Jhydroxyandrostenedione, 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 1 3-hydroxyandrostenedione being the main testicular product vs. 11 -ketotestosterone dominating in the blood, may indicate that 11 3-hydroxyandrostenedione is converted to 11 -ketotestosterone at extratesticular sites.

SEX STEROIDS AND SPERMATOGENESIS IN THE AFRICAN CATFISH (CLARIAS GARIEPINUS)

“…Furthermore, the blood plasma sex steroid levels were quantified during the same period by specific radioimmunoassay [10].…”

“…10 weeks of age with the initiation of rapid spermatogonial proliferation. Testicular development proceeds through four main stages that are characterized histologicaly [10,11] by the presence of spermatogonia (stage I), spermatogonia and spermatocytes (stage II), spermatogonia, spermatocytes and spermatids (stage III), and finally all germ cells stages including spermatozoa (stage IV). Usually, most males will be in stage IV at ca.…”

Testicular apoptosis in feral Clarias gariepinus using TUNEL and cleaved caspase-3 immunohistochemistry

“…Clarias gariepinus is a resilient bottom-dwelling indigenous African teleost species, whose testicular steroid biosynthesis activities are also well described (Schulz et al, 1996; [Cavaco et al, 1997] and [Cavaco et al, 1998]). The testes of species such as C. gariepinus and other amniotes are also useful model systems to study toxicant actions stage-by-stage during spermatogenesis.…”

The lack of endocrine disrupting effects in catfish (Clarias gariepinus) from a DDT sprayed area

“…The influence of the natural reproductive stage of the fish, could have also played a role in influencing the interpretation of the gonad condition. In both biomarkers, the gonad condition was strongly influenced by the number of developing and mature fish present (Cavaco et al, 1997). In the LF there were more specimens classified as developing (with inherently low gonad mass) than mature specimens, which probably resulted in the under estimation of the gonad condition.…”

“…It can be used to estimate the degree of effects on reproduction, based on the assumption that a reduction in relative gonad mass can occur in response to increased contaminant exposure (Schweer, 2002). It has successfully been used in C. gariepinus, however, is largely influenced by environmental conditions (DeGraaf and Janssen, 1996;Cavaco et al, 1997;Yalcin et al, 2001). To remove this strong influence, Packard and Boardman (1999) recommended an alternative, using a more statistically sound methodology involving ANCOVA.…”