Source of F series prostaglandins during the early postpartum period in cattle

In vivo and in vitro studies were conducted to determine the contribution of the bovine uterus to concentrations of 15-keto-13,14-dihydro-prostaglandin F2 alpha (PGFM) in peripheral plasma of postpartum cows. In Experiment 1, cows were assigned to three groups: untreated control (n = 4), hysterectomy following a manually induced prolapse of the uterus (n = 5) and sham operation (n = 3: prolapse of the uterus and replacement). Surgery was performed within 8 h of parturition, and blood samples collected frequently on the day of surgery and once (0800 h) or twice (0800 and 1700 h) daily from Day 1 to Day 15 postpartum. Following hysterectomy, PGFM concentrations decreased precipitously, became essentially undetectable by 5 h, and remained so for the rest of the experimental period. In contrast (P less than 0.01), PGFM concentrations, which remained elevated during the day of surgery in the sham-operated group, peaked on Day 2 (sham-operated group: 1339 pg/ml) or Day 3 (untreated control: 2143 pg/ml), and declined to a basal concentration between Days 10 to 15. In Experiment 2, in vitro metabolism of tritiated arachidonic acid ([3H] AA: 10 microCi) and production of PGF2 alpha and PGFM were studied in explants of early postpartum intrauterine tissues (myometrium, caruncle and intercaruncular endometrium). Extracts of [3H] AA metabolites released into the incubation medium were separated on Sephadex LH-20 column chromatography. Metabolites of [3H] AA, having the same chromatographic mobility as PGF2 alpha, PGFM and PGE2, were detected.