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

Platelet-activating factor (PAF) is a phospholipid mediator with potent bio logical 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 antioxida nt enzyme activities and on duodenal muscle contractility. The effects of h yperbaric oxygenation (HBO2) on the response to PAF were also investigated. Two experimental sets were designed. Each experimental set comprised two g roups 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 gro up. Blood samples and duodenum segments of both groups were obtained 2 h af ter the administration of PAF or SP. We observed that acetylcholine (ACh)-i nduced duodenal muscle contractions were more effective in the PAF group th an those in the control group. Erythrocyte catalase and glutathione peroxid ase (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 sign ificantly increased. We found that erythrocyte GPx activities were lower an d erythrocyte superoxide dismutase activities were higher than in the contr ol group. These data support the hypothesis that PAF produces free oxygen r adicals and that HBO2 enhances this effect.