Progestin Receptors in the Brain and Pituitary of the Bonnet Monkey (Macaca radiata): Differences between the Monkey and the Rat in the Distribution of Progestin Receptors*

Abstract

Using the radiolabeled synthetic progestin [3H] R5020, putative progestin receptors have been identified by Sephadex LH-20 gel filtration and density gradient centrifugation in soluble cytosol fractions of uterus, pituitary gland, and brain of the bonnet monkey (Macaca radiata). These receptors had a high affinity for [3H]R5020 (Kd = 0.3 nm) and sedimented at 6–7S in 10% glycerol, 5–20% sucrose gradients. [3H]R5020 binding was inhibited more than 70% by 25-fold molar excesses of progesterone or other physiologically active synthetic progestins but was unaffected by estradiol, corticosterone, dexamethasone, or testosterone. In ovariectomized monkeys, the progestin receptors were restricted to the hypothalamus and preoptic area; no receptors were detected in cingulate or parietal cortex, amygdala, midbrain, brainstem, or cerebellum. When ovariectomized monkeys were implanted with estradiol-containing Silastic capsules to generate serum levels of this hormone in the physiological range, cytosol progestin rec...