THE EXPRESSION OF CYTOSOLIC PHOSPHOLIPASE-A2 AND PROSTAGLANDIN ENDOPEROXIDE SYNTHASE IN OVINE MATERNAL UTERINE AND FETAL TISSUES DURING LATE-GESTATION AND LABOR

Gene expression of cytosolic phospholipase A2 (cPLA2) and prostaglandi n endoperoxide synthase(PGHS) 1 and 2 was studied in ovine maternal ut erine and fetal tissues during glucocorticoid induced premature labor and spontaneous labor and compared with gestational age matched contro ls not in labor. Northern blot analysis demonstrated that the messenge r RNA (mRNA) abundance of cPLA2 and PGHS-2, but not PGHS-1, increased significantly in the endometrium during both glucocorticoid induced pr emature labor and spontaneous labor. Protein levels of the two enzymes measured by Western blot analyses were also elevated in the endometri um during glucocorticoid induced premature labor. cPLA2 mRNA was detec ted in the myometrium, but no difference was observed between ewes in labor and their gestational age matched controls not in labor. While t he level of PGHS-2 mRNA was below detection in the myometrium with the methods used, the enzyme protein for PGHS-2 in the myometrium was sig nificantly increased in both glucocorticoid induced premature labor an d spontaneous labor. Using immunocytochemical methods, PGHS-2 enzyme p rotein was identified in the endometrial gland epithelial cells and my ometrial cells. PGHS-2 mRNA was also detected in the ovine fetal cotyl edons in which no differences for PGHS-2 mRNA existed between tissues collected from ewes in labor and ewes not in labor. In contrast, there were no detectable signals for cPLA2 or PGHS-2 mRNA in either amnion or chorion. We conclude that the ovine endometrium and myometrium, but not fetal membranes, are important tissue sites of prostaglandin bios ynthesis involved in the process of ovine parturition.