The expression of cyclooxygenase-2 (COX-2) in amnion and decidua following spontaneous labor

Prostaglandins production rises dramatically during term and preterm labor. The source of this production is thought to be the fetal membranes and maternal decidua. The enzyme responsible for the conversion of arachidonic acid to the prostaglandins and related endoperoxides is variously known as prostaglandin synthase or cyclooxygenase (COX). An inducible form of this enzyme, COX-2, has been described in several tissues. The purpose of this study was to investigate a possible role for COX-2 in labor by comparing the COX-2 content in amnion and decidua from laboring and non-laboring patients.

Fetal membranes from seven normal labor and ten elective cesarean sections at term were collected immediately following delivery. The maternal age and gravity were similar between the groups. The amnion and decidua were identified, washed in sterile saline, frozen in liquid nitrogen and stored in -70 degrees C. COX-2 expression was determined using Western Blot analysis with a purified COX-2 antibody. A scanning densitometer was used to quantify the bands. Results were expressed as mean +/-S.D. ng/50 micrograms protein.

The concentration of COX-2 in amnion of laboring women showed a twofold increase (240.0 +/- 17.6 vs. 120.7 +/- 5.1) compared to the non-labored group (p < 0.05). The concentration in the decidua showed no significant increase during labor (38.1 +/- 7.5 vs. 26.4 +/- 2.1, p > 0.05).

We evaluated the role of COX-2 in normal labor. Our study demonstrates that COX-2 is significantly induced in the amnion following spontaneous labor. These findings suggest that the induction of amnion COX-2 may be involved in the process of human labor.