THE ROLE OF NA+ H+ EXCHANGE IN ISCHEMIA-REPERFUSION/

In ischemia the cytosol of cardiomyocytes acidifies; this is reversed upon reperfusion. One of the major pH(i)-regulating transport systems involved is the Na+/H+ exchanger. Inhibitors of the Na+/H+ exchanger h ave been found to more effectively protect ischemic-reperfused myocard ium when administered before and during ischemia than during reperfusi on alone. It has been hypothesized that the protection provided by pre -ischemic administration is due to a reduction in Na+ and secondary Ca 2+ influx. Under reperfusion conditions Na+/H+ exchange inhibition als o seems protective since it prolongs intracellular acidosis which can prevent hypercontracture. In detail, however, the mechanisms by which Na+/H+ exchange inhibition provides protection in ischemic-reperfused myocardium are still not fully identified.