Effect of hysterectomy on luteinizing hormone-induced corpora lutea of pseudopregnant rabbits

Mature New Zealand white female rabbits were mated to vasectomized males (day of mating = Day 0 of pseudopregnancy). On Day 9 of pseudopregnancy rabbits were injected with either 1 ml of saline or 15 µg of luteinizing hormone (LH) in 1 ml of saline to produce a second set of corpora lutea. This dose of LH is less than that required to induce luteolysis of the original corpora lutea. Rabbits were autopsied on Day 12, 15, 18, 21, 24, or 30. Corpora lutea of saline-injected control rabbits and the original corpora lutea of LH-injected rabbits reached maximum size by Day 9, started to regress after Day 15, and were significantly reduced in size by Day 21. The induced corpora lutea in the LH-injected rabbits grew only until Day 15, when they were 6 days old, at which time the induced corpora lutea were one-half the weight of the original corpora lutea in the same ovary. The induced corpora lutea maintained their weight from Day 15 to 21 and then decreased in size. Other rabbits were hysterectomized on Day 4 of pseudopregnancy and injected with LH on Day 9. The life of the original corpora lutea was prolonged to 24 days. In contrast to the regression of induced corpora lutea in intact rabbits, induced corpora lutea increased slightly in weight between Day 15 and 24, indicating that the uterus not only influences regression of the corpora lutea of pseudopregnant rabbits but may also influence luteal development.