Comparison of the Luteolytic Action of LH and Estrogen in the Hamster

Luteal morphology and maintenance of decidual cell response (DCR) or pregnancy were used as end-points in evaluating the effects of bovine luteinizing hormone (NIH-LH-B3) on the corpora lutea (CL) of the hamster. Daily treatment for 5 days with 20 to 100 μg of LH induced luteal regression in pseudopregnant and pregnant animals. However, 50 μg of LH also caused hyperplasia and hypertrophy of the ovarian interstitium which resulted in a positive DCR in pseudopregnant animals despite the involution of the CL. One hundred μg of LH consistently induced ovulation in pseudopregnant and occasionally in pregnant animals. The CL resulting from new ovulations were nonfunctional. FSH, prolactin or a combination of FSH and prolactin did not induce luteolysis. The luteoly-tic effect of 100 μg of LH was counteracted by prolactin, but not FSH. The ratio of exogenous prolactin and LH was critical for the preservation of the CL. Treatment with combinations of prolactin and LH in ratios of 2.5, 10 and 20 preserved CL in 37....