Submission Number: SEI-4-35-27
Abstract Number: 403
THE ROLE OF EPIDERMAL GROWTH FACTOR IN THE REGULATION OF PROSTAGLANDIN PRODUCTION IN THE UTERINE ENDOMETRIUM IN CATTLE.
Laboratory of Theriogenology, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Japan 1
Objective of the study is to determine the role of epidermal growth factor (EGF) in uterine prostaglandin (PG) production in cattle, with the hypothesis that EGF acts as a luteotrophic factor by increasing the ratio of luteotrophic PGE2/luteolytic PGF2 produced in the endometrium. First, profiles of EGF and its mRNA levels were determined by EIA and quantitative RT-PCR, respectively, in the uterine endometrium during the estrous cycle using 37 Holsteins culled by reasons other than infertility. EGF concentrations showed two peaks on days 2-3 (estrus=day 0) and days 13-14. The concentrations remained high (10-15 ng/ml) after day 14 in uterine horns with an embryo, while the concentrations decreased to basal levels (0.5-2 ng/ml) by day 16 in uterine horns without an embryo. EGF mRNA levels increased after the estrus and maintained at intermediate levels between day 3 and day 12, and further increased on days 13-14. The increased levels of EGF mRNA were maintained till day 20 in uterine horns with an embryo, while the levels declined to basal levels by day 16 in the horns without an embryo. Then, the effect of human recombinant EGF (hrEGF) and anti-EGF antibody on endometrial PGE2 and PGF2 production was determined in endometrial tissues obtained on days 15-17 from uterine horns with or without an embryo. Endometrial tissues (about 50 mg) were treated for 12 h with either 10 ng/ml hrEGF or 0.1 g/ml antibody. Amount of PGs in culture media was determined by EIA. In endometrial tissues from uterine horns with an embryo, hrEGF increased PGE2/PGF2 ratio by 8-fold compared to non-treated control, by increasing and decreasing PGE2 and PGF2 production, respectively. In contrast, hrEGF had no effect on PGE2/PGF2 ratio, but increased production of the two PGs in tissues from uterine horns without an embryo. Antibody suppressed production of the two PGs to about 40% of control in endometrial tissues of the both origin. These results suggest that endometrial EGF concentrations are maintained at high levels by the presence of embryos after day 14 of estrus, and that the levels of EGF may contribute to maintain corpus luteum by increasing the ratio of PGE2/PGF2 production in the endomtrium.
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