Effects of platelet-activating factor and hyperbaric oxygenation on antioxidant defense and duodenal contractility

Platelet-activating factor (PAF) is a phospholipid mediator with potent biological effects on organisms. Some investigators have previously postulated that PAF exerts its effects by producing oxygen free radicals. The aim of this study was to investigate the effects of PAF on intracellular antioxidant enzyme activities and on duodenal muscle contractility. The effects of hyperbaric oxygenation (HBO2) on the response to PAF were also investigated. Two experimental sets were designed. Each experimental set comprised two groups and each group consisted of six animals. The first group of the first experimental set to which only isotonic NaCl solution (serum physiologic, SP) was injected was named the control group. The second group of the first experimental set to which only PAF was administrated was named the PAF group. Blood samples and duodenum segments of both groups were obtained 2 h after the administration of PAF or SP. We observed that acetylcholine (ACh)-induced duodenal muscle contractions were more effective in the PAF group than those in the control group. Erythrocyte catalase and glutathione peroxidase (GPx) activities were found to be lower. In the second experimental set, rats administered PAF, and rats administered SP were exposed to HBO2. In both groups of this set, contractile responses to ACh were found to be significantly increased. We found that erythrocyte GPx activities were lower and erythrocyte superoxide dismutase activities were higher than in the control group. These data support the hypothesis that PAF produces free oxygen radicals and that HBO2 enhances this effect.