Immunocytochemical localization of prostaglandin synthase in the ovine uterus during the oestrous cycle and in early pregnancy.

Prostaglandin (PG) synthase has been localized by immunocytochemistry within the ovine uterus throughout the oestrous cycle and in early pregnancy. On Day 4 of the cycle, PG synthase was located primarily in the stromal cells in caruncular and intercaruncular tissue with little staining in the epithelium. On Days 14 through to 16, the most intense staining was in the luminal epithelial cells (caruncular and intercaruncular) and in epithelial cells of glands close to the uterine lumen. PG synthase was also located in the intercaruncular stromal cells, particularly close to the myometrium. Staining for the enzyme on Day 10 was intermediate between that of Day 4 and Day 14. On Day 15 of pregnancy, the pattern of staining was identical to that on Day 15 of the cycle, with no detectable difference in intensity. When endometrial cells (cycle, Day 14) were cultured with and without ovine trophoblast protein-1 (3 ng mL-1) in vitro, release of PGE and PGF2 alpha was attenuated (54% and 47% of control respectively) but no differences were observed in the intensity of staining for PG synthase in the cells. These results demonstrate marked cyclical changes in the endometrial cell types producing PGs, suggesting differential regulation of PG synthase. In addition, it appears that conceptus-induced changes in PGF2 alpha release do not occur via changes in the concentration or cellular localization of PG synthase, but rather that the activity of the enzyme is modified.