Suppression of 20α-hydroxysteroid dehydrogenase activity in cultured rat luteal cells by prolactin

Abstract

20α-Hydroxysteroid dehydrogenase (20α-SDH) activity increases in the cycling corpus luteum of the rat, beginning at 14.00 h on the day of diestrus, but remains low in corpora lutea of pregnancy throughout the first 19 days of gestation. When cells derived from 7-day-old corpora lutea of pregnant rats were cultured for 7 or 12 days, there was a spontaneous rise in 20α-SDH activity from an initial value of 0.44 ± 0.27 to 4.1 ± 0.7 units/mg supernatant protein. Addition of LH (NIH-S-18; 2.0 μg/ml) or prostaglandin F 2α(2.8 × 10 −5 M) to the medium from day 4 to the end of the incubation period caused a slight but significant reduction in 20α-SDH activity (20%, P < 0.05). Supplementation of the medium with ovine prolactin (NIH-P-S11; 10.0 μg/ml) from the time of seeding or from the 2nd to 4th day of culture reduced the activity of 20α-SDH measured on day 12 by 61% ( P < 0.001). This finding suggests that the suppression of 20α-SDH by prolactin, hitherto demonstrated only in vivo, results from a direct action of the hormone on the luteal cell.