Sarcolemmal destabilization and destruction after ischaemia and reperfusion and its relation with long-term recovery of regional left ventricular function in pigs.

This study investigated the relation between the extent of morphological damage, observed 2 hours after reperfusion which followed either 30 or 60 minutes of ischaemia, and the long-term recovery of regional myocardial function after the same periods of ischaemia. The nature of the morphological changes in this in vivo pig model is akin to that described in an in vitro Langendorff preparation. It is shown that sarcolemmal disruption, after 60 minutes of ischaemia followed by reperfusion, is associated with aggregation of sarcolemmal intramembranous particles and formation of multilamellar, lipidic structures suggesting a reorganization of the phospholipids, lateral phase separation and fusion events. However, thirty minutes of ischaemia with reperfusion did not lead to sarcolemmal disruption although extrusion of lipidic material, observed in a fraction of the mitochondria in each muscle cell, occurred independent of the duration of ischaemia. In another group of animals the regional myocardial function was assessed by cross-sectional echocardiography after 2 weeks of recovery. This correlated with the degree to which sarcolemmal integrity in the biopsies was maintained. The observed destruction of the sarcolemma was best explained in terms of bilayer destabilization, mediated by an increase in calcium and hydrogen ions in the cytosol of the myocardial cell.