Synthesis of LH-RH by rat hypothalamic tissue in vitro. II. Effect of short-term orchiectomy and estradiol benzoate therapy.

Normal, castrate and estradiol benzoate (EB; 1 microgram/100 g b.w. x 6d, s.c.)-treated castrate male rats were utilized to study the short term effects of these treatments upon the incorporation of 3H-glycine into LH-RH in vitro. The rise in serum LH and FSH observed in the untreated castrates was prevented by EB therapy. The treatment had no significant effect upon serum LH-RH levels or the incorporation of 3H-gly into LH-RH. EB treatment markedly (p less than 0.01) increased the hypothalamic LH-RH concentration and significantly lowered the specific activity (nCi/ng) of the 3H-gly-LH-RH (p less than 0.05). These results suggest that EB acts both on the pituitary and hypothalamus to suppress gonadotropin (Gn) release, but that, at the time period studied, neither castration or EB-treatment had any apparent effect upon hypothalamic LH-RH synthesis.