H2O2-INDUCED OXIDATIVE INJURY IN RAT CARDIAC MYOCYTES IS NOT POTENTIATED BY 1,1,1-TRICHLOROETHANE, CARBON-TETRACHLORIDE, OR HALOTHANE

Free radical-induced oxidative stress has been linked to ischemia-repe rfusion injury of the myocardium. The .OH radical is considered the mo st damaging radica and can be increased in cells by treatment in vitro with H2O2. The purpose of the present study was to determine if aliph atic halocarbons enhance H2O2-induced oxidative injury in isolated car diac myocytes from neonatal rats. Oxidative damage was assessed by mea suring release of thiobarbituric acid-reactive substances (TBARS) from lipid peroxidation, loss of lactate dehydrogenase (LDH) through damag ed sarcolemmal membranes, and alterations in intracellular calcium ([C a2+]i) transients in electrically stimulated (1 Hz, 10 ms, 60 V) myocy tes. H2O2 increased TBARS release and LDH leakage in a concentration-d ependent (20-200 muM) manner. Continuous suffusion with H2O2 first alt ered the configuration of [Ca2+]i transients, then eliminated them, an d finally caused [Ca2+]i overload (basal [Ca2+]i exceeded peak systoli c [Ca2+]i of control). The time to [Ca2+]i overload was inversely asso ciated with concentration, and the shortest time to overload was obtai ned with 100 muM H2O2. A 1-h preincubation of myocytes with the iron c helator deferoxamine inhibited all effects of H2O2. 1,1,1-Trichloroeth ane, carbon tetrachloride, or halothane at 1 mM significantly and reve rsibly reduced [Ca2+]i transients but did not influence TBARS release or LDH leakage. Simultaneous exposure of myocytes to H2O2 and halocarb ons did not affect the myocyte response to H2O2 exposure. Results indi cate that the three halocarbons tested do not enhance H2O2-induced oxi dative injury in isolated cardiac myocytes.