Measurements of pituitary lh content, uterine wet and dry weights, and ovarian and pituitary wet weights were obtained for each day throughout pseudopregnancy in the hamster, and were compared with comparable data obtained during the oestrous cycle.
Ovarian weights increase during pseudopregnancy, reflecting activation of corpora lutea; they remain higher than oestrous cycle values even after ovulation recurs, reflecting delayed involution of the corpora lutea. Ovarian weight does not show a regular cycle during pseudopregnancy, in contrast with the regular changes seen during the oestrous cycle.
Uterine wet and dry weights continue to manifest a 4-day periodicity during pseudopregnancy, a finding which parallels oestrous cycle values but at a higher level.
During pseudopregnancy pituitary lh content rises, reaching a peak level on the 7th day; a significant drop occurs at the time of the ovulation at the end of pseudopregnancy. The rise exceeds that seen during the oestrous cycle and correlates with the block to ovulation in pseudopregnancy. Pituitary weights are higher than in cyclic animals, but do not show cyclic changes.