NITRIC-OXIDE MEDIATES PLATELET-ACTIVATING-FACTOR STIMULATORY ACTION ON UTERINE PROSTAGLANDIN PRODUCTION

Accumulated evidence suggests that platelet-activating factor (PAF) ma y have a role in implantation by stimulating prostaglandin (PG) produc tion. Since we had demonstrated that nitric oxide (NO) can increase ut erine PGs, the aim of this study was to explore whether or not NO coul d mediate rat uterus responses to PAF on day 5 of gestation, when impl antation takes place. Uterine motility was enhanced by PAF as compared to controls. This action was abolished by either the arginine analogu e, N-monomethyl L-arginine (L-NMMA) or the cyclooxygenase inhibitor, i ndomethacin. On the other hand, NOS activity was detected in uterine s trips and could be stimulated by PAF. The cyclooxygenase product PGE(2 ) was also significantly stimulated by PAF. Inhibition of endogenous N O formation abolished the PAF effect on PG synthesis, Our results sugg est that NO is an important intermediate in the interaction between PA F and PGs.