EFFECT OF TRIIODOTHYRONINE ADMINISTRATION ON ESTROGEN-RECEPTOR CONTENTS IN PERIPUBERAL SERTOLI CELLS

The effects of thyroid hormone on androgen metabolism in peripuberal S ertoli cells through the inhibition of estradiol production have been reported previously. It was our intention to investigate further the p ossible role of thyroid hormone on the interaction between testicular steroids and Sertoli cells by analyzing the effects of triiodothyronin e (T-3) On. estrogen receptor content in 2-, 3- and 4-week-old euthyro id rats. Triiodothyronine treatment (3 mu g/100 body wt per day) given during the last week prior to sacrifice resulted in reduced testicula r growth in 2-week-old animals. Sertoli cells from all groups were cul tured initially under basal conditions for the first 24 h and subseque ntly in the presence of testosterone and/or T-3 for the additional 24 h. The in vitro addition of T-3 induced a decrease of estrogen recepto rs (ERs) in 2- and 3-week-old animals that appeared more pronounced es pecially in the presence of T-3 and testosterone. When T-3 was tested in vivo we noticed that the decrease of ER content was even greater in all three groups under the in vitro influence of both T-3 and testost erone. In 3-week-old animals a simultaneous assay of ERs in both nucle ar and cytoplasmic compartments was performed. The ER concentrations i n the nucleus were closely related to those of the cytoplasm. The in v ivo administration of T-3 was responsible for a greater decrease of ER s in the nucleus than in the cytosol. On the basis of these results, a nd in agreement with our previous data, we speculate that the effect o f T-3 in the maturational events of Sertoli cells could involve both e stradiol production and ER content.