Pathophysiology of the puerperal period: relationship between prostaglandin E2 (PGE2) and uterine involution in the cow

Eighteen Holstein cows were randomly assigned to a control group or a treatment group on the day after parturition (Day 0). The treatment started on Day 10 and consisted of intrauterine infusion of 20 micrograms of 16,16 dimethyl PGE2 (dPGE2) in 6 ml of sterile physiologic saline or saline alone (control) twice a day, for 7 days. Palpation per rectum was performed twice weekly to assess utero-ovarian morphological changes. Blood samples were collected before, during and after the treatment for the assay of 13,14-dihydro-15 keto-PGF2 alpha (PGFM), 13,14-dihydro-15 keto-PGE2 (PGEM), and progesterone concentrations and the proliferative activity of peripheric lymphocytes in vitro. At 20 +/- 1 days post partum, animals were slaughtered and the genital tract was evaluated macroscopically. Caruncles from both horns were taken for measurement of tissue content of PGF2 alpha and PGE2 caruncles from the former gravid horn were taken for in vitro culture. Endometrial secretions were taken for bacteriology and assay of immunoglobulins (Ig's). Treatment with dPGE2 affected many of the macroscopic characteristics used to evaluate uterine involution such as the tone (P<0.001), length (P<0.01) and the weight (P<0.05) of the uterus. Follicular development was also affected (P<0.05), principally on the ovary contralateral to the previously gravid horn. This treatment also inhibited lymphoblastic transformation response to concanavalin A (P<0.01), phytohemagglutinin and pokeweed mitogen (P<0.06), decreased both IgG (P<0.01) and IgM (P<0.05) concentrations in the secretions from the previously nongravid and gravid uterine horns, respectively, and increased (P<0.05) the incidence and severity of uterine infections, specifically those caused by Actinomyces pyogenes. The ratio of plasma prostaglandin concentration (PGFM/PGEM) was affected by treatment. After in vitro culture of caruncular tissue for 6 hours there was no significant difference between the two groups for the synthesis of PGF2 alpha, and PGE2. These results suggest that PGE2 impedes uterine involution in the cow.