抄録
After AI, the majority of sperm are removed from the uterus by degradation, evacuation and phagocytosis by recruited polymorphonuclear neutrophils (PMNs). We hypothesized that PMNs are migrating also into bovine oviduct fluid under physiological condition. The objective of this study was to investigate the possible mechanism to regulate the behavior of PMNs to sperm in oviduct environment toward ovulation in cows. Leukocytes (60% for PMNs and 40% for lymphocytes) were observed in bovine oviduct fluid. Experiment 2, bovine oviduct epithelial cells (BOEC) were cultured for 24 h and the supernatant was used for 4 h incubation with PMNs from cow blood. Phagocytosis was then assayed by co-incubation of these PMNs with capacitated sperm. BOEC culture supernatant suppressed phagocytosis of PMN to sperm (23%) vs. control medium (33%), and LH-stimulated BOEC supernatant further suppressed it (15%).experiment 3, LH stimulated PGE2 secretion in BOEC culture.Exp. 4, PGE2 dose-dependently (10–6 to 10–8 M) suppressed PMN phagocytosis to sperm. Exp. 5, EP2 receptor antagonist (AH6809) weakened the inhibition of PGE2 on PMN phagocytosis to sperm (28% vs. 19.8% for PGE2 alone). Moreover, AH6809 weakened the inhibition of phagocytosis by LH-stimulated BOEC supernatant (22.5% with AH6806 vs. 15% without AH6806). The results indicate that sperm are facing PMN in the oviduct under physiological condition, and PGE2 in the oviduct fluid stimulated by the LH-surge appears to play a major role in PMN suppression via EP2 receptor. Thus, bovine oviduct supplies microenvironment by PGE2 to protect sperm from phagocytosis of PMNs toward ovulation, thereby supporting the occurrence of fertilization.
