Sarcolemmal integrity during ischaemia and reperfusion of the isolated rat heart

The effects of ischaemia and reperfusion on sarcolemmal permeability were studied in the isolated rat heart using an ionic lanthanum probe technique. Detection of increased permeability after exposure to short periods of ischaemia without accompanying reperfusion effects was achieved by employing a substrate-free, low calcium saline solution as vehicle for ionic lanthanum. Quantifiable results showed a rapid increase in sarcolemmal permeability in the subendocardium after 15 min of ischaemia, with the subepicardium showing similar alterations after longer periods. Reperfusion after 15 min of ischaemia led to recovery of normal permeability characteristics, correlating well with ultrastructural and functional recovery. Reperfusion after 25 min of ischaemia did not allow recovery of sarcolemmal permeability, ultrastructure, or function. These results show a clear correlation between the development of irreversible myocardial damage and increased sarcolemmal membrane permeability.