The growing evidence for a correlation between the hormonal dependence of neoplastic tissues and the presence of specific hormone receptors led us to investigate the possible presence of specific progesterone receptors in dimethyl benzanthracene (DMBA)-induced mammary tumors in the rat. After homogeneisation in 3 vol (w/v) of 25 mM Tris-HC1 (pH 7.4), 1.5 mM EDTA, 10 mM thioglycerol and 10% glycerol (buffer A), the 105,000 xg super-natant was used for binding studies with the highly potent syn-thetic progestin [3H] R 5020 (17, 21-dimethyl-l9-nor-pregna-4, 9-diene-3, 20-dione). Specificity of [3H] R 5020 binding was studied by both sucrose gradients and charcoal adsorption. As evidenced by sucrose gradient analysis, specific binding of [3H] R 5020 is associated with components migrating at 6–7S and 4–5S. Unspecific binding of the synthetic progestin at 4S is eliminated by pretreatment with dextran-coated charcoal. [3H] R 5020 binding is easily displaced by unlabeled R 5020, progesterone, norgestreal, chlormethindrone and norethindrone. 17β-estradiol, diethylstilbestrol, testosterone, dihydrotestosterone, dexame-thasone and cortisol have little, if any effect on [3H] R 5020 binding.
KeywordsGrowth Hormone Thyrotropin Release Hormone Anterior Pituitary Cell Estradiol Benzoate Estradiol Benzoate
Unable to display preview. Download preview PDF.