Factors Affecting Uptake of Estradiol-6,7-3H by the Hypophysis and Hypothalamus

The uptake of labeled estradiol by the anterior hypothalamus and the anterior hypophysis was depressed by the concomitant injection of 1.8 or 4 μg of unlabeled estradiol. In contrast, the treatment had little or no effect on the uptake of estradiol in the cerebral cortex and cerebellum. The labeled estradiol taken up initially by the hypothalamus and hypophysis was not removed by the subsequent injection of unlabeledunlabeled steroid. In contrast to 17β-estradiol, pretreatment with 17α-estradiol, even in large amounts, did not alter the uptake of 17β-estradiol by the anterior hypothalamus and hypophysis. These results provide further evidence for specific estradiol-binding receptors of limited capacity in the anterior hypothalamus and anterior hypophysis. (Endocrinology80:1133,1967)