Maintenance of Ovine Corpora Lute a in the Absence of Ovarian Follicles

Experiments were conducted todetermine whether ovarian follicles play a role in regulating the life span of the ovine corpusluteum. Destruction of follicles by X-irradiation of ovaries increased the efficacy of continuous infusion of purified LH to prolong the life span of the corpus luteum of the anatomically intact ewe. When follicles were present, the amount of infused LH required to maintain corpora lutea was 4 times greater than that needed when follicles had been destroyed. Infusion of 300 μg LH/day/ewe maintained fully functional corpora lutea provided no rapidly growing follicles were present; this dose increased the concentration of LH in serum by less than 2 ng/ml. The pattern of spontaneous luteal regression in ewes whose follicles were destroyed differed significantly from the abrupt luteal regression which occurred between days 15 and 17 after heat in nontreated cyclic ewes. In the absence of follicles, corpora lutea regressed gradually, and luteal degeneration was nearly complete by day 20. It was concluded that ovarian follicles, and thus follicular estrogen, are not required for maintenance of the corpus luteum of the ewe. Furthermore, we suggest that follicles may compete with corpora lutea for luteotrophin, and that the preovulatory maturation and development of follicles play a role in instigating the demise of the corpus luteum of the cyclic ewe. (Endocrinology87:1228, 1970)