Effect of estradiol on testicular function in Rhinella arenarum (Amphibia, Anura)

SCAIA MARIA FLORENCIA; CEBALLOS NORA RAQUEL

Congreso; 27th Conference of European Society for Comparative Endocrinology; 2014

Rhinella arenarum is an anuran of the Bufonidae family with a dissociated reproductive pattern. Unlike species of the Ranidae family, in adult males estradiol (E2) is not produced by the testis. This difference is related to the presence of the Bidder Organ, which is characteristic of bufonids and is the main source of circulating E2 in this species. In the toad, plasma E2 has a seasonal pattern, with the highest concentrations determined during the reproductive (R) and post-reproductive (PostR) seasons (Scaia et. al, J. Exper. Zool, 319A:355-364, 2013). Although the effect of E2 on testicular physiology has been investigated in frogs, the role of E2 on testicular steroidogenesis and spermatogenesis in bufonids still remains unexplored. In this study we analyze seasonal variations in the effect of E2 on testicular steroidogenic enzymes and testicular apoptosis and proliferation in adult males of R. arenarum. Testicular tissue was incubated for 24hs without or with 2nM and 20nM E2, being 2nM the concentrations determined during the R season. Enzymatic activities of cytochrome P450 17-hydroxylase, 17-20 lyase (CypP450c17) and 3beta-hydroxysteroid dehydrogenase/isomerase (3beta-HSD/I) were determined using radioactive pregnenolone in the presence of NADPH and NAD+ as cofactors, respectively. Apoptosis and proliferation were analyzed in testicular fragments before and after E2 incubations, using TUNEL fluorescent kit and BrdU detection kit, respectively. Our results indicate that there is no significant effect of E2 on 17-hydroxylase and lyase activities of CypP450c17. Regarding 3beta-HSD/I, E2 decreases enzymatic activity only during the PostR season with no effect during the pre-reproductive (PreR) and R seasons. Apoptotic spermatocytes were observed in E2-treated testicular fragments from the R season, but not from the PreR seasons. Finally, BrdU-positive-stained nucleus in control and E2-treated fragments from the R season correspond to spermatogonias. These results suggest that E2 could be involved in the regulation of 3beta-HSD/I and testicular apoptosis-proliferation balance. In conclusion, E2 concentration corresponding to R season could be responsible for the apoptosis of the advanced spermatogenic cists and could be involved with the proliferation of new spermatogonia.