INHIBITION OF NA+/H+ EXCHANGER ATTENUATES NEUTROPHIL-MEDIATED REPERFUSION INJURY

Background. The effect of Na+/H+ exchange inhibition in neutrophil-induced reperfusion injury was investigated using a new amiloride analogue, 5-methyl-N-isobutyl amiloride (MIA). Methods. Rat neutrophils were separated using Percoll gradient. Luminol chemiluminescence intensity of isolated neutrophils was depressed by MIA in a dose-dependent manner. Results. The effect of MIA on neutrophil-induced reperfusion injury was evaluated in Langendorff-perfused rat hearts subjected to 30 minutes of normothermic ischemia. Postischemic left ventricular developed pressure recovery was depressed by the reperfusion with neutrophils (60% +/- 7% to 33% +/- 26%) and was reverted by MIA pretreatment (86% +/- 17%, p < 0.05). MIA also improved percent recovery of coronary flow (51% +/- 2% to 70% +/- 13%), reduced creatine kinase (0.28 +/- 0.1 to 0.085 +/- 0.03 IU.L-1.g(-1) dry wt), and lactate dehydrogenase leakage (10.6 +/- 3.8 to 5.16 +/- 1.3 IU.L-1.g(-1) dry wt) significantly. The incidence of reperfusion-induced ventricular fibrillation also was reduced by MIA. Conclusions. The inhibition of Na+/H+ exchange shows a protective effect against neutrophil-induced reperfusion injury possibly by inhibiting the activation of neutrophils.