Testosterone and oestradiol in concert protect seminiferous tubule maturation against inhibition by GnRH-antagonist.

Oestradiol enhances follicle stimulating hormone (FSH) action on seminiferous tubule maturation, but the relative involvement of oestradiol and testosterone remains unclear. This study compares the influences of oestrogen and androgen in FSH and testosterone-deficient rats. Animals were injected daily GnRH-antagonist alone (Ant) or combined with 17β-oestradiol benzoate (EB), or testosterone propionate (TP), or both from post-natal day (pnd) 5 to 15. Hormone levels, tubule growth, cell numbers, germ cell apoptosis and proliferation, and Sertoli cell maturation were evaluated on pnd 16. Ant decreased serum FSH and testosterone levels to ∼60% and ∼50% of control values, respectively, and decreased tubule growth, Sertoli cell number and maturation. Germ cell number declined by apoptosis. Co-administration of EB stimulated spermatogonia proliferation and maintained FSH levels (86% of control). Tubule growth, Sertoli cell number and spermatocyte apoptosis remained normal after TP co-administration, but Sertoli cell maturation, germ cell number and spermatogonia survival were reduced. Co-administration of EB with TP prevented all inhibitions. In conclusion, administration of oestradiol with testosterone, but neither one alone, protected seminiferous tubule maturation against inhibition caused by Ant-induced disruption. Oestrogen was involved in stimulating germ cell proliferation and the maintenance of Sertoli cell maturation, whereas androgen affected seminiferous tubule growth and spermatocyte survival.