SARCOLEMMAL PHOSPHOLIPID ASYMMETRY AND CA FLUXES ON METABOLIC INHIBITION OF NEONATAL RAT-HEART CELLS

The present study examines the hypothesis that during depletion of hig h-energy phosphates a change will occur in the phospholipid topology a nd in Ca fluxes in cultured neonatal cells and that these two events m ay be causally related. A combination of 2-deoxyglucose and iodoacetic acid was used to produce graded changes in the adenine nucleotides in the cells. An on-line technique for Ca-45 measurement was used to fol low Ca uptake and compartmentation by the cells, and chemical and enzy matic probes were used to study sarcolemmal phospholipid topology. Aft er 15 min of metabolic inhibition (ATP = 10% of control) an increase i n cellular Ca occurs, which progresses with time. Over 70% of this Ca accumulates in the mitochondria. After 30 min of metabolic inhibition (ATP <10% of control) a change in the phospholipid topology is observe d, and an increased amount (two times control) of sarcolemmal phosphat idylethanolamine is present in the outer monolayer of the sarcolemma. This change in phospholipid topology was independent of the extra-cell ular Ca concentration. The sequence of altered Ca fluxes and distribut ion followed by the altered phospholipid topology is discussed in term s of its possible role in the pathogenesis of sarcolemmal disruption.