Oxygen-derived free radical-mediated injury occurs frequently following prolonged ischemia and reperfusion. Recently, the nonglucocorticoid steroid U74006F has been shown to exert therapeutic effects presumably secondary to its peroxide inhibitory effect. This experiment investigates the effect of pretreatment with U74006F on H2O2 induced cardiac oxidative stress and lipid peroxidation. Myocardial performance was determined in a modified Langendorf model. Adult male Sprague-Dawley rats were pretreated with U74006F (3 mg/kg iv) or saline vehicle 30 min prior to cardiac excision. The hearts were then placed into a closed isolation chamber and perfused with oxygenated Krebs-Henseleit solution for a 30-min equilibration period. Oxyradical challenge consisted of the addition of 200 or 400 microM H2O2 to the perfusate for 60 min. Contractile activity was continuously monitored; perfusate glutathione, lactate dehydrogenase, and headspace ethane were collected every 30 min for 90 min. A decrease in lipid peroxidation was seen in animals pretreated with U74006F when exposed to 200 microM H2O2; higher oxyradical loads overwhelmed this protective effect. Glutathione efflux was increased in both groups and not affected by treatment. Late LDH efflux and myocardial contractility were improved by pretreatment with the drug. These results suggest that pretreatment with U74006F significantly decreases oxyradical mediated myocardial lipid peroxidation during moderate oxyradical challenge and may improve cellular function.