Lung oxidant changes after zymosan peritonitis: relationship between physiologic and biochemical changes.

Our purpose was to determine the effect of non-bacteria-dependent systemic inflammation on the degree and time course of lung oxidant activity and antioxidant defenses, comparing these changes with lung, physiologic, and histologic alterations. Adult male rats were given intraperitoneal zymosan (0.7 mg/g body weight) and were fluid resuscitated. Oxidant changes were measured as lung tissue oxidized glutathione (GSSG) and malondialdehyde (MDA) content, antioxidant defenses as tissue reduced glutathione (GSH), and catalase. Animals were killed at 4, 12, and 24 h, and at 5, 10, and 30 days. Lung data were compared with that found in liver. We noted a 45% mortality in the first 18 to 36 h with all remaining animals surviving. In the first 24 h, we noted a doubling of lung MDA and an 80% conversion of tissue GSH to GSSG compared with less than 5% in control animals, indicating a severe oxidant stress. These findings corresponded with marked increase in lung neutrophils. Arterial pressure (Pa(O2)) was significantly decreased from a control of 95 +/- 4 mm Hg to 80 +/- 5 mm Hg and 75 +/- 4 mm Hg at Days 5 and 10, respectively, but returned toward control by 30 days. Lung GSSG and MDA remained significantly increased for the 30-day period, whereas amounts of the antioxidants, catalase, and GSH returned to control after 24 h. The ongoing oxidant stress corresponded with marked mononuclear cell infiltration and interstitial thickening, which persisted over the 30-day period even after peritonitis had completely resolved. In contrast, liver GSSG was only transiently increased, and MDA remained at control values, whereas liver antioxidants, GSH, and catalase decreased significantly to 50% of control value for at least 10 days. We conclude that lung oxidant injury is initiated by acute peritonitis and appears to be perpetuated by ongoing lung inflammation, even after systemic inflammation resolves. Despite malnutrition and ongoing oxidant stress, there is a rapid restoration and maintenance of lung antioxidant activity.