Effects of Testosterone Propionate and Estradiol Benzoate—Alone or in Combination—on Serum LH and FSH in Orchidectomized Rats

In adult rats, the post-castration rise in serum LH and FSH 5 days following orchidectomy was prevented by daily subcutaneous injections of testosterone propionate (@100 μg/100 g body wt) or estradiol benzoate (@1 μg/100 g body wt). No differential effects on LH and FSH release were observed following treatment with either steroid. No significant changes in serum gonadotropin levels were produced by treatment with testosterone propionate over a range of 0.001-15 μg or by treatment with 0.00008-0.1 μg estradiol benzoate. Synergism between testosterone propionate and estradiol benzoate was not observed when 4 doses of testosterone propionate (0.15, 1.5, 15 and 30 μg/100 g) were given in combination with each of 4 doses of estradiol benzoate (0.0025, 0.025, 0.25 and 0.5 μg/100 g). However, all 4 doses of testosterone propionate antagonized the gonadotropin inhibiting action of the highest dose of estradiol benzoate. Concentrations of LH and FSH in sera of orchidectomized, adrenalectomized rats were indisting...