Lysophosphatidylcholine induces Ca2+-independent cellular injury attenuated by d-propranolol in rat cardiomyocytes

In isolated rat cardiomyocytes, exogenous lysophosphatidylcholine (LPC) (15 mu M) increased the intracellular Ca2+ concentration ([Ca2+](i)) from 72 +/- 5 to 3042 +/- 431 nM accompanied by cell injury as indicated by the hypercontracture of the cells and the increase in creatine phosphokinase (CPK) release. In order to understand whether the cell injury induced by LPC was a consequence of the elevation of [Ca2+](i), the effect of LPC was examined in the Ca2+-free solution containing EGTA. Under the Ca2+-free conditions, LPC did not increase [Ca2+](i), whereas it still inflicted injury on the cells in terms of cell-shape change and CPK release to the same degree as that under the Ca2+-present condition. Addition of ryanodine (10 mu M) failed to prevent the changes in cell-shape and CPK release induced by LPC under both Ca2+-free and Ca2+-present conditions. Preincubation of the myocytes with d-propranolol (50 mu M) inhibited the LPC-induced changes in cell-shape and CPK release under both Ca2+-free and Ca2+-present conditions (p < 0.05). Our study provides clear evidence that the cellular injury induced by LPC could be independent of the increase in [Ca2+](i), and the Ca2+-independent cellular injury induced by LPC could be attenuated by d-propranolol, although the mechanism remains unknown.