STRUCTURAL-CHANGES IN FREEZE-FRACTURED SARCOLEMMA OF ISCHEMIC MYOCARDIUM

Abstract

Ultrastructural alterations in the sarcolemma of ischemic myocardium were studied with the freeze-fracture technique. In normal dog myocardial sarcolemma, the P fracture face contained many intramembranous particles which were randomly distributed, while the E fracture face had few intramembranous particles; no structural abnormalities were seen within the lipid bilayer on either face. Myocardium ischemic for 45 min displayed no, or only slight, aggregation of intramembranous particles, but upon reperfusion for 5-20 min, the particles became significantly aggregated in the P face. Scattered nicks within the lipid bilayer were observed on both fracture faces. Intramembranous particles were similarly aggregated in myocardium ischemic for 2 h. The number of nicks were greatly increased on the P and E fracture faces. These structural alterations which were undetected in thin sections, are likely to be associated with altered function in the sarcolemma of ischemic myocardium.