Dynamics of ovarian blood supply to periovulatory follicles of the ewe.

Radioactive microspheres were injected into the ovarian artery ipsilateral to the ovary containing the dominant (preovulatory) or postovulatory follicle of the ewe to estimate the distribution of ovarian blood to those follicles throughout the periovulatory period. The follicle of interest was excised from the ovary at the first sign of estrus (4-h heat checks), or 4, 8, 12, 16, 20, 24, 28 and 32 h later. Blood samples to be analyzed for serum luteinizing hormone (LH) were taken at each observation for estrus. Follicles were partitioned into basal tissue, apical tissue and fluid (preovulatory follicles) constituents. Radioactivity was determined within the residual ovary and in each follicular component. Follicular data were normalized to the ascending limb of the preovulatory surge of serum LH (first detected increase in LH = O h). The supply of ovarian blood to the wall (apex + base) of follicles was elevated after the rise in LH was initially ascertained (0-12 h). The distribution of blood to the follicular wall began to decline from 12 to 16 h, and subsequently continued to decrease (20 h) until after ovulation had occurred (greater than or equal to 24 h after the LH increase). Blood supply was less to the wall of follicles in the 20-h group and to ruptured follicles than that to the wall of follicles collected before the initiation of the surge of LH. There was no evidence that blood supply to either the basal or apical portion of the follicular wall was altered preferentially. Radioactivity was not detectable within follicular fluid.