[Changes in the number of estradiol and testosterone-binding sites of the hypophysis in cyclic female rats in the period of elevated follicle-stimulating hormone levels].

The level of the cytoplasmic and nuclear estradiol and testosterone receptors was investigated in the female rat hypophysis in various time-intervals of proestrus and estrus. The highest concentration of the nuclear and androgenic receptors was noted in the afternoon at the P stage during the preovulatory release of LH and FSH. After a short-term decrease in the number of the nuclear estradiol- and testosterone-binding sites at 9 and 11 p.m. at the P stage which was taking place in parallel with a decrease in the blood level of LH and FSH, their significant rise was noted at 1 and 3 a.m. at the E stage during the second wave of FSH release. However the concentration of the nuclear estrogenic receptors in these hours at the E stage was 3.5 times lower, and that of the androgenic receptors a 1.4-fold lower than their concentration at 7 p.m. at the P stage. It was assumed that the adenohypophyseal estrogenic and androgenic receptors were involved in the stimulation of the second FSH wave.