[Progesterone level in the peripheral blood and the cytosol progesterone receptor in the uterine mucosa and myometrium of sows during the estrous cycle].

Parallel radioimmunological determinations of progesterone level in the peripheral blood and of the content of the cytosolic receptor of this hormone in cells of the mucosa and muscular coat of the uterus were carried out in a group of 25 sexually mature sows on the 0, 13, or 17 day of the sexual cycle. The concentration of the receptor was determined by the carbon-dextran method. The greatest amount of the receptor was found in both tissues studied on the 0 cycle day (307.1 +/- 39 fmole/mg of protein and 395.6 +/- 57 fmole/mg of protein in the mucosa and muscular coat, respectively) at a simultaneously low level of progesterone in the peripheral blood. The lowest concentration of the receptor was found in the muscular coat on the 13 day, and in the mucosa on the 17 day. A negative correlation was shown between progesterone level in the peripheral blood and the receptor content in the muscular coat. A similar correlation was shown in the mucosa on the 0 and 13 day, but it was absent on the 17 cycle day. The occurrence of a large amount of specific progesterone receptor was also shown in the uteri of sexually immature sows. The values of stable association of the progesterone-receptor complex in the uterus tissues of sexually mature sows averaged: 1.95 +/- 0.33 X 10(8) M-1, whereas of immature sows: 1.14 +/- 0.14 X 10(8) M-1.