We have determined binding sites for
estrogen,
progestin,
androgen and
glucocorticoid in anterior pituitaries from Sprague-Dawley rats, a strain with low
estrogen sensitivity, and in
diethylstilbestrol-induced
pituitary tumors in Fischer 344 rats, a strain with high
estrogen sensitivity. Binding sites differ in their quantity and subcellular distribution. Cytosolic sites for [3H]
estradiol in normal pituitaries from untreated rats were high prevailing over sites for other
hormones, but they were depleted in the
tumors due to their retention in nuclei under the influence of
estrogen. Unoccupied nuclear sites for
estrogen in normal glands also prevailed over sites for other
steroids, and were similar to those in
tumors. Second, the
progestin site labeled with [3H]
R 5020 was concentrated 5.7-fold in cytosol and 8.5-fold in nuclei of the
tumors over the values found in glands from normal males estrogenized for 3 days. Third,
glucocorticoid receptors labeled with [3H]
dexamethasone were predominantly cytosolic in normal glands, but very low in cytosol and more evident in nuclear extracts from the
tumors, the reverse of the profile found in normal pituitaries. Last, limited and comparable amounts of
androgen receptors were measured in the subcellular fractions of both tissues. It is suggested that the subcellular distribution of some
steroid receptors may be controlled in part by the cell population of the tissue and its degree of genetic activity.