Demonstration and Characterization of Estrogen Receptor in Chimpanzee Sex Skin: Correlation between Nuclear Receptor Levels and Degree of Swelling*

Abstract

The presence of cytosol and nuclear estrogen receptors has been demonstrated in chimpanzee sex skin. Both receptors sedimented at approximately 4S in sucrose gradients containing 0.6 M KC1. Both had a steroid specificity and high affinity for estrogen that conform to an estrogen receptor. The absence of such receptors in the pigmented skin surrounding the sex skin and in the abdominal skin indicates their discrete localization in the sex skin. While the cytosol receptor remained low (<10 fm/mg cytosol protein), the nuclear estrogen receptor showed a fluctuation during the menstrual cycle, attaining the highest level during the late follicular phase (90.4 ± 8.4 fmol/mg nuclear extract protein; nearly 3–4 times the level during the early folliculax and luteal phases). When ovariectomized animals were treated with mestranol, the concentration of nuclear estrogen receptor increased from below detection to 74 fmol/mg nuclear extract protein. An increase in serum progesterone during the luteal phase, despite concurrently elevated serum estradiol levels, was associated with a reduction of the nuclear estrogen receptor as was the administration of progesterone and mestranol to estrogen-primed ovariectomized animals. Changes in the concentration of the nuclear estrogen receptor were positively correlated with changes in the degree of the sexual swelling. These results strongly suggest that estrogen controls the sexual swelling by acting through specific receptors in the sex skin, and that counteraction by progesterone of estrogen stimulation of the sexual swelling is effected through a reduction in nuclear estrogen receptors.