Evidence for Preferential Transfer of Prostaglandin F2α to the Ovarian Artery Following Intrauterine Administration in Cattle1

The effect of sectioning the broad ligament ipsilateral to the corpus luteum on estrous cycle length was evaluated. This surgical procedure isolated the region of proposed transfer of the uterine luteolytic factor from uterine venous input. The estrous cycles of four of five animals were prolonged to at least 30 days, as judged by plasma progesterone concentrations and the presence of marked corpora lutea at laparotomy on Day 30. In a second experiment, one of the branches of the ovarian artery was cannulated in the hilus of the ovary in five dairy cows, and 6 mg of prostaglandin F2α (PGF2α) was injected into the lumen of the uterine horn ipsilateral to the cannula on Days 12 or 13 of the cycle. Frequent samples were collected simultaneously from the ovarian artery, carotid artery, and jugular vein. The concentration of prostaglandins of the F series (PGF) was observed to increase rapidly at all three sampling sites following administration of PGF2α. While the concentration was highest in the carotid and jugular within 5 min of treatment, the concentration of PGF continued to increase in the ovarian artery to reach a peak 40 min after treatment and remained at levels significantly greater (p < 0.05) than jugular or carotid levels for 80 min. These data are consistent with the hypothesis of preferential transfer of a uterine luteolytic factor from the uterus to the ovarian artery. Intrauterine administration of 6 mg of PGF2α was luteolytic, as judged by a fall in plasma progesterone concentrations and a mean corpus luteum weight of 1.83 ± 0.22 g upon termination of the experiment 72 h after treatment. Peripheral plasma estrone and estradiol-17β levels were observed to increase to a peak 9 h after treatment, after which a slight increase in the mean plasma LH concentration occurred. Ovulation had occurred in four of five animals by 72 h after treatment, although LH peaks of the usual preovulatory magnitude were not observed to precede ovulation in all animals.