The Effects of Blocking Androgen Receptor: Activation on Porcine Sertoli Cell Proliferation and Maturation.

Abstract

Proliferation and maturation of Sertoli cells is a major determinant of sperm production. Understanding the function of androgens during Sertoli cell proliferation and maturation is the long term goal of this research. The current objective is to determine the effects of blocking androgen receptor activation during the first wave of Sertoli cell proliferation. In the pig, Sertoli cell proliferation occurs in two waves, which begin postnatally and continue until just before puberty. During Sertoli cell proliferation, androgens were thought to be relatively quiescent. Work in rodent models suggests that androgens are required for normal Sertoli cell maturation following the proliferative phase. We propose that blocking androgen binding to the androgen receptor during the first wave of Sertoli cell proliferation will stimulate Sertoli cell proliferation. To evaluate this, pairs of littermate male pigs were treated daily with flutamide, which is a non steroidal anti-androgen or with canola oil vehicle from 1 week of age until 6.5 weeks of age, covering the first interval of Sertoli cell proliferation. Blood was collected weekly from animals to analyze hormone levels. Tissues were recovered at 6.5 weeks (n=3) immediately following treatment or at 11 weeks (n=3) of age, 4.5 weeks after treatment. Testosterone was measured using radioimmunoassay and Sertoli cell numbers were counted using GATA4 immunohistochemistry. Circulating plasma testosterone was on average six times greater in the flutamide-treated animals compared with the vehicle treated littermates. Increased testosterone is an indicator that flutamide effectively blocked androgen receptor activation. After treatment with flutamide, there was a two-fold increase in testes size and a two-fold increase in Sertoli cell numbers at 6.5 weeks, suggesting a role for testosterone in Sertoli cell proliferation, contrary to previous thoughts. At 11 weeks of age, however, the animals treated with flutamide exhibited no significant difference in Sertoli cell numbers compared with the vehicle controls. Increased understanding of endogenous hormone action will provide a better understanding of the factors controlling Sertoli cell proliferation and ultimately the hormonal control of fertility. Research supported in part by NRI 2008-35203-19082 from USDA NIFA, Kellogg, Hatch, and W2171 funds. (poster)