Effect of free radical scavengers on diaphragmatic contractility in septicperitonitis

We investigated the effects of polyethylene glycol-adsorbed superoxide dism utase (PEG-SOD), polyethylene glycol-adsorbed catalase (PEC-CAT), and DMSO on diaphragmatic contractility and malondialdehyde (MDA) concentrations in septic peritonitis in vitro. One hundred eighty-six rats were divided into two groups. One group (CLP group) was treated with cecal ligation and perfo ration (CLP), and the other (sham group) was treated with laparotomy. PEG-S OD, PEG-CAT, and DMSO were administered intraperitoneally 30 min before and 12 h after CLP. The left hemidiaphragm was removed at 10 h or 16 h after t he operation. We assessed the diaphragmatic contractility by twitch charact eristics and force-frequency curves in vitro. We measured MDA concentration s, as an index of oxygen-derived free radical-mediated lipid peroxidation, and the activities of two main antioxidant enzymes, superoxide dismutase (S OD) and glutathione peroxidase (GPx), as an index of antioxidant defenses, after CLP. Diaphragmatic force generation capacity was significantly reduce d after CLP. Diaphragmatic: MDA levels were significantly elevated after CL P. PEC-SOD, PEG-CAT, and DMSO significantly improved diaphragmatic contract ility and prevented the elevation in diaphragmatic MDA concentrations after CLP. Diaphragmatic SOD activities were significantly increased after CLP. These results suggest that several types of oxygen-derived free radicals pl ay a role in the reduction in diaphragmatic contractility after CLP.