Luteinizing hormone, prolactin and ovarian 20 -hydroxysteroid dehydrogenase levels during pregnancy and pseudopregnancy in the rat.

Abstract

Ovarian α—hydroxysteroid dehydrogenase (α—OH—SDH) activity and serum and pituitary concentrations of luteinizing hormone (LH) and prolactin were determined in individual rats at selected times during the estrous cycle, normal pseudopregnancy, prolonged pseudopregnancy due to hysterectomy or induced deciduomata, and pregnancy. During die 5-day cycle, α—OHSDH activity was lowest at diestrus II (38.8 ± 2.5 mU enzyme/mg protein), increased 2-fold at proestrus, then declined at estrus (52.8 ± 4.8). Except for sharp peaks at proestrus, serum LH and prolactin levels were consistently low at diestrus and estrus (mean ± SE over 3 days of diestrus = 15.5 ± 1.4 ng LH/ml serum and 48.1 ± 3.1 ng prolactin/ml serum). During normal pseudopregnancy, enzyme activity on Day 1 was comparable to that found at diestrus II of the cycle, then declined 3-fold at Day 6. After Day 6, α— OH—SDH increased steadily until Day 13 (60.9 ± 4.6 mU/mg protein). From Days 1-6, enzyme levels in pregnant rats were quite similar to those in no...