Effects of steroid hormones on spermatogenesis and GnRH release in male Leopard frogs, Rana pipiens

Effect of estradiol on apoptosis, proliferation and steroidogenic enzymes in the testes of the toad Rhinella arenarum (Amphibia, Anura)

“…Our results in R. arenarum indicate that in spite of the season, estradiol has no effect on spermatogonial proliferation. Similarly, but using an in vivo approach, Tsai et al (2003) were not able to detect any stimulatory effect of E 2 in L. pipiens after 20 days of treatment. However, it is important to take into account that there are differences in the experimental approaches employed in all the species studied.…”

“…In X. laevis, larval exposure to E 2 induces an acceleration of spermatogenesis by increasing the percent of spermatocytes, spermatids and spermatozoa (Hu et al, 2008). Otherwise, in L. pipiens estrogens retard the formation of secondary spermatogonia and spermatocytes and accelerate the final stages of spermatogenesis (Tsai et al, 2003). Furthermore, E 2 is associated with high mitogenic activity of spermatogonia in P. esculentus (Fasano et al, 1989;Rastogi et al, 1985;Varriale et al, 1986) via Fos and mitogen-activated kinase (Chieffi et al, 1995(Chieffi et al, , 2000Cobellis et al, 1997Cobellis et al, , 1999Cobellis et al, , 2002Minucci et al, 1997).…”

“…Moreover, during the reproductive season of P. esculentus, there is a strong relationship between high levels of testosterone, the mitotic activity of the germinal epithelium and the expression of c-kit, which is indispensable for spermatogenesis and spermatogonial proliferation (Raucci and di Fiore, 2007). Furthermore, in Lithobates pipiens corticosterone induces a reduction in spermatid formation, while 5a-dihydrotestosterone reduces the amount of secondary spermatogonia and spermatids, and stimulates spermatocytes formation (Tsai et al, 2003).…”

“…Moreover, in juveniles Xenopus laevis estradiol (E 2 ) induces an acceleration of spermatogenesis (Hu et al, 2008). In L. pipiens, the action of chronic estradiol may be both inhibitory and stimulatory, depending on the stages of spermatogenesis, since chronic treatment retards the formation of spermatocytes and secondary spermatogonia, and accelerates the latter stages of spermatogenesis (Tsai et al, 2003). Besides, in P. esculentus there is a strong mitogenic activity of spermatogonia in the period of the year characterized by high concentrations of estradiol (Fasano et al, 1989;Rastogi et al, 1985;Varriale et al, 1986).…”

Assessing the physiological sensitivity of amphibians to extreme environmental change using the stress endocrine responses

“…Even a common ecological research practice, toe clipping, can decrease plasma levels of testosterone in Rhinella marina (Narayan et al 2011). In addition, treatment with exogenous corticosterone depresses plasma androgen levels (Moore and Zoeller 1985, Paolucci et al 1990, Narayan et al 2011, reduces spermatogenesis (Biswas et al 2000, Tsai et al 2003, and inhibits reproductive behavior Miller 1984, Leary et al 2006; for a review, see Leary 2009). The inhibition of male courtship behavior by CORT can occur within minutes; therefore, it is likely mediated by nongenomic mechanisms involving signal transduction coupled to membrane glucocorticoid receptors (Orchinik et al 1991, for a review, see Carr 2011).…”