Abstract
Further characteristics of androgen and estrogen receptors from male rat pituitary cytosol were studied. Following ultra-centrifugation in a linear sucrose gradient (5–20%) two radioactive peaks for testosterone were observed, one at the top of the gradient, and one in the 7–8 S region. For dihydrotestosterone there were also two peaks one in the 3–4 S region, the other in the 7–8 S region. Only the 7–8 S peaks were specific for androgens. Under the same conditions, estradiol-17β exhibited only one peak in the 8–10 S region. When rats were previously castrated, an increase of the 7–8 S peak for testosterone and for dihydrotestosterone was observed. Thus, orchidectomy did not abolish androgen receptors in pituitary cytosol. It was likely that androgen and estrogen receptors were proteins. Indeed, the hormone-receptor binding was abolished to a great extent by proteolytic enzymes action. Taking into account some characteristics of these receptors: dissociation constants, specific binding capacity, sedimentation constants, sensitivity to heat or to enzyme action, it seemed easy to differentiate androgen receptors from estrogen receptors. Thus, it was concluded that pituitary cytosol from male rats contained two kinds of receptors, one for androgens, and one for estrogens. Contrarily, it is not certain at the moment that there are two androgen receptors, one for testosterone and one for dihydrotestosterone, or that there is only one receptor for both hormones.
Published Version
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