Effects of Testosterone Administration on Testis and Serum Concentrations of Estradiol-17β in Immature Rats1

Abstract

Rat Sertoli cells produce estrogen (E₂) in vitro when testosterone (T) is added to the medium. Our experiments sought to establish if the rat testis had this capability in vivo. Twenty-one-day-old rats were injected with T (6.25-200 µg. s.c./g BW) and killed 3 h later. Estradiol-17β was determined by RIA of samples which were first chromatographed on Sephadex LH-20. Rats injected with 50 or 100 µg/g BW of T had serum and testis E₂ concentrations significantly greater than animals injected with smaller or larger doses of T or oil-treated controls and the 50 µg dose was more effective than the 100 µg dose. Animals castrated 12 h before being identically treated with a 50µ g/g BW dose of T, showed an increase in serum E₂ which was not different from this response in the intact animal, indicating the testes of 21-day-old rats do not contribute significantly to the elevated serum E₂ levels seen after injection of T in the intact rat. Injection of E₂ (5 ng/g BW) into 21-day-old rats elevated serum E₂, but did not alter testis E₂ content. It is concluded the the prepubertal testis responds to exogenous T with increased E₂ formation, most of which remains in the testis for at least 3 h.