[The influence of N-nitro-L-arginine methyl ester (L-NAME) on hydroxyl free radical formation in the post-ischemic reperfused heart of anesthetized rats].

N-nitro-L-arginine methyl ester (L-NAME) has been reported to have protective action against hydroxyl free radicals. We have investigated whether L-NAME influences free radical formation in the post-ischemic reperfused heart of anesthetized rats. An isolated rat heart-lung preparation was used. Forty male Wistar rats were allocated into D (D-NAME 100 microMol.l-1), L (L-NAME 100 microMol.l-1), LH (L-NAME 100 microMol.l-1 and 1MAC halothane), LI (L-NAME 100 microMol.l-1 and 1MAC isoflurane), and LS (L-NAME 100 microMol.l-1 and 1MAC sevoflurane) groups. The heart was perfused initially at the cardiac output of 30 ml.min-1 and the atrial pressure of 70 mmHg. Drugs were administered into the reservor 7 min after the start of perfusion. Ten minutes after the start of perfusion, the heart was rendered globally ischemic for 10 min by reducing the preload and afterload to zero and then reperfused for 10 min. At the end of reperfusion, the heart was freeze-dried for 4 days. The perfusate blood was collected just before and after ischemia and at the end of reperfusion. The formation of hydroxyl radicals in the perfusate blood and heart was measured with high-performance liquid chromatography using salicylic acid. Hydroxyl radicals react with salicylic acid, yielding dihydroxybenzoic acid (DHBA). Before and after ischemia, there were no significant differences among the groups in cardiac output, systolic pressure, heart rate, and right atrial pressure. DHBAs in the heart of L, LH, LI, and LS groups were significantly lower than those of D group. However, there were no differences in the DHBA levels among 4 groups. The concentrations of DHBA in the perfusate blood after ischemia and reperfusion were significantly higher than those before ischemia in all groups. DHBAs in the perfusate blood after ischemia and reperfusion of L, LH, LI, and LS groups were significantly lower than those of D group. However, there were no differences in the DHBA levels among 4 groups administered L-NAME. This study indicates that L-NAME reduces hydroxyl free radical formation in the post-ischemic reperfused heart in anesthetized rats and volatile anesthetics do not influence the depressant effect of hydroxyl free radical formation by L-NAME.