ORGANIZATION AND FUNCTION OF SARCOLEMMAL PHOSPHOLIPIDS IN CONTROL ANDISCHEMIC-REPERFUSED CARDIOMYOCYTES

The topic of this review is the lipidic part of the sarcolemma, the pl asma membrane of the myocardial cell, and its role in (dis)function of the cardiomyocyte. First the isolation of the sarcolemma and its lipi d composition are discussed, These phospholipids are not randomly dist ributed over the two monolayers of the lipid bilayer and negatively ch arged phospholids are exclusively present in the cytoplasmic leaflet o f the sarcolemma, which also contains the majority of phosphatidyletha nolamine. This distribution is most likely caused by an active transpo rt of these lipids and by an interaction of the headgroup of these lip ids with the cytoskeleton. Subsequently the physicochemical properties of sarcolemmal phospholipids are discussed, where it is shown that ce rtain phospholipids prefer non-bilayer phases, and the effects of sarc olemmal phospholipids on trans-sarcolemmal ion fluxes and calcium comp artmentation are discussed. In the second part the effect of ischemia on sarcolemmal phospholipids is discussed with regard to: transbilayer distribution, hydrolysis, lateral distribution and sarcolemmal bilaye r stability. In our view, onset of ischemia initiates a sequence of ev ents leading to a loss of normal sarcolemmal phospholipid distribution with an outward migration of phosphatidylethanolamine. There follows, as ischemia progresses, loss of sarcolemmal bilayer stability due to the expression of the non-bilayer behavior of phosphatidylethanolamine , leading to irreversible disruption of the sarcolemma and cell death.