Studies on luteolysis: effect of antiserum to luteinizing hormone on sterols and steroid levels in pregnant hamsters

Abstract

The effect of luteinizing hormone antiserum (LH A/S) on sterol and steroid levels in luteal and non-luteal ovarian compartments, and on serum steroid levels of pregnant hamsters, was studied. Injection (ip) of 0.1 ml of LH A/S on day 7 caused termination of pregnancy and morphological regression of the corpus luteum (CL) within 18-20 h of treatment, whereas LH-free non-immune serum had no effect. Within 3 h of administration of LH A/S the luteal progesterone levels fell from a control value of 36.0 ± 2.4 to 15.6 ± 3.4 ng/mg, and estrogen from a control value of 20.8 ± 3.4 to 12.2 ± 1.5 pg/mg. By 12 h progesterone had dropped to 7.3 ± 0.3 ng/mg whereas estrogen was undetectable by radioimmunoassay. Serum progesterone fell in 3 h from 5.53 ± 0.39 to 3.15 ± 0.26 ng/ml whereas estrogen fell from 172 ± 26 to 123 ± 9 pg/ml. The progesterone content of non-luteal ovarian tissue dropped in 3 h from 1.06 ± 0.01 to 0.47 ± 0.06 ng/mg and estrogen from 115.0 ± 1.5 to 11.0 ± 0.65 pg/mg. Both progesterone and estrogen were undetectable at 24 h. In the CL, free cholesterol concentration did not change significantly after A/S treatment, while esterified cholesterol increased from 2.82 ± 0.14 to 4.14 ± 0.25 μg/mg within 6 hand 5.52 ± 0.17μg/mgby 12 h. The results suggest that LH plays a critical role in the maintenance of CL of early pregnancy in the hamster and that deprivation of LH, even for periods as short as 3 h, significantly influences steroid production. The accumulation of cholesterol esters following LH-deprivation suggests that loss of cholesteryl esterase activity could be one of the events leading to luteolysis.