This larger band was successfully blocked by incubation with the immunizing peptide showing it is a form of PON2. The reduced placental expression of PON2 protein expression found in labour in the middle site would be likely to promote inflammatory processes. Thus it is possible that a reduction in PON2 protein may help to initiate or promote labour but this is speculative. Why PON2 mRNA was found to be increased may seem paradoxical but it may be that the increased mRNA is a separate response to oxidative stress as a result of myometrial contractions. The reduction in PON2 protein could also be due to processes other than reducing mRNA synthesis, such as increased protein degradation. PONs are glycosylated with high-mannose-type sugars, which are important for protein stability but are not essential for their enzymatic activities. Whether alterations in glycosylation of PON2 could affect PON2 expression in the placenta would require future BI-6C9 research. Oxidative stress occurs when the production of reactive oxygen species overwhelms the intrinsic anti-oxidant defenses. At the moment it is not clear whether the Ifetroban sodium observed reduction in PNO2 protein expression in the placenta in the labour group is a consequence of labour itself or, alternatively, contributed to labour via endocrine, hemodynamic or other processes. Since human patients have been used it is difficult to separate these effects. It is known however that contraction of the uterus leads to ischemicreperfusion injury that can alter placental protein expression. Furthermore Doppler ultrasound studies have demonstrated an inverse relationship between uterine artery resistance and the intensity of uterine contractions during labour. It has been shown in chronically instrumented pregnant rhesus monkeys that placental blood flow is almost completely stopped during sustained myometrial contractions and that this occurs as a result of compression of the arcuate and spiral arteries. The closest human model to this was performed on patients prior to termination of pregnancy at 17�C20 weeks of gestation. During oxytocin-induced contractions, a 50% reduction in flow into the intervillous space, as well as a fall in entry sites and volume, was found compared to when no contractions occurred. This suggests that intermittent perfusion of the intervillous space would lead to an ischemic-reperfusion injury of the placenta. Reactive oxygen species and the oxidant/antioxidant balance can be affected as a result.