Uterine prostaglandin-forming cyclooxygenase: relationship to luteolysis and subcellular localization

The concentration of cyclooxygenase protein in uterine caruncles is increased on days 13 to 15 of the ovine estrous cycle prior to decreases in plasma progesterone concentrations and at the same time when increases in uterine luteolysin (PGF2 alpha) secretion are reported to occur. This finding suggests that luteolysin synthesis is controlled, in part, by the activity of the cyclooxygenase. All caruncular cell types stain positively for cyclooxygenase antigenicity and thus can form prostaglandin endoperoxides. The cyclooxygenase in a model cell type, mouse 3T3 cells, has been localized on the endoplasmic reticulum and nuclear membrane using an immunocytochemical method.