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.