Effects of unilateral ovariectomy before and after mating on growth of corpora lutea and peripheral progestagen concentrations in pregnant rats.

Unilateral ovariectomy was performed on 20 rats 4-5 wk before mating (ULO-B group), and 18 rats 8 days after mating (ULO-A group); 16 rats were maintained as controls. The effects on growth of individual corpora lutea (CL) in the remaining ovary and peripheral blood progestagen concentrations were examined. CL hypertrophy was observed by Day 13 in the ULO-B group and by Day 16 in the ULO-A group. Progesterone and 20 alpha-dihydroprogesterone concentrations were double control values at Day 16 in the ULO-B group, but half the control values in the ULO-A group. The CL hypertrophy and increased progestagen concentrations in the ULO-B group occurred despite crowding due to a doubling of the normal number of CL within the remaining ovary.