Ontogeny of testicular inhibin and activin in ducks: An immunocytochemical analysis

Abstract

The ontogeny of testicular inhibin/activin in ducks was investigated. Testicular localization of three inhibin/activin subunits (α, β A and β B ) was determined in embryonic and newly hatched ducks from 12 days of incubation to 1 day of age, in immature ducks and in adult ducks. In the duck embryonic testis, positive α-subunit immunostaining was first detected in the Leydig cells and Sertoli cells on day 15 of incubation, whereas β A -subunit and β B -subunit immunostaining were found in Sertoli cells and primary germ cells on day 18 of incubation. In 1 month old ducks, intense staining of α-subunit was present in the seminiferous epithelium consistent with localization in Sertoli cells and primary germ cells, and the immunostaining of the β A -and β B -subunit was also present in Sertoli cells and primary germ cells. Specific immunostaining with inhibin/activin α-, β A -and β B -subunits antisera occurred in Sertoli cells in the adult duck testes. In conclusion, it was shown that, in the duck testis, the majority of α-, β A -and β B -subunits are colocalized in Sertoli cells with a certain degree of staining in germ cells and the α-subunit is present in Leydig cells of embryonic testes before day 18 of incubation. These results indicate that Sertoli cells and possibly germ cells in the embryonic testes of late stage of incubation and newly hatched ducks, immature ducks and mature ducks may produce bioactive inhibin dimers, inhibin A and inhibin B, as a possible regulator of follicle-stimulating hormone secretion. Free inhibin/activin subunits and their dimers may also play an autocrine/paracrine role in the development of the testis and spermatogenesis. Furthermore, early onset of the αsubunit in duck testes indicates that it may have an autocrine/paracrine effect on steroid hormones, which is important for sex differentiation.

Circulating inhibin and testosterone during sexual maturation and reproductive seasonality of captive male killer whales (Orcinus orca)

“…However, one of the testicular hormones, inhibin has not been investigated in male killer whales. Inhibin is a glycoprotein hormone secreted by the gonads in mammals (Medan et al, 2007, Chaichanathong et al, 2017, birds (Akashiba et al, 1988, Yang et al, 2005a, 2005b, 2005c, and some Cetaceans, such as beluga (Katsumata et al, 2012) and bottlenose dolphin (Katsumata et al, 2017).…”