Luteotropic influence of the ovine uterus

Preliminary observations indicated that the ovine uterus might play a contributing role in the development of the corpus luteum. In order to better define this putative relationship, we monitored luteal function in mature ewes that were hysterectomized or sham-operated at different intervals following induction of ovulation. Corpora lutea formed following hysterectomy carried out immediately after ovulation were subnormal. Circulatory concentrations of progesterone in these animals began to ascend normally, but then achieved a plateau level less than that of control animals. This was attributed to reduced size of the luteal gland, and not to anomalies per unit tissue in morphology or content of progesterone. Luteal activity was not altered in ewes hysterectomized later in the estrous cycle (Day 5). However, when such a luteal phase was terminated by exogenous luteolysin, corpora lutea formed subsequently were defective. It appears that the ovine uterus produces a hormonal factor during metestrus that augments the growth potential of the corpus luteum.