PHOSPHOLIPASE A(2) IS NOT RESPONSIBLE FOR LYSOPHOSPHATIDYLCHOLINE-INDUCED DAMAGE IN CARDIOMYOCYTES

Lysophosphatidylcholine (LPC) is known to increase the intracellular c oncentration of Ca2+ ([Ca2+](i)), leading to cell damage. In the prese nt study we examined whether LPC activates phospholipase A(2) (PLA(2)) and whether the activation of PLA(2) is responsible for the LPC-induc ed cell damage in isolated rat cardiomyocytes. LPC (15 mu M) produced an increase in [Ca2+](i), a change in cell shape from rod to round, an d the release of creatine kinase (CK) accompanied by a significant ele vation of the cellular level of nonesterified fatty acids (NEFA), espe cially arachidonic acid. Three PLA(2) inhibitors, 7,7-dimethyl-(5Z,8Z) -eicosadienoic acid (DEDA), 3-(4-octadecylbenzoyl)acrylic acid (OBAA), and manoalide, attenuated the LPC-induced accumulation of unsaturated NEFA to a similar degree. Nevertheless, whereas both DEDA and OBAA at tenuated the LPC-induced increase in [Ca2+](i), change in cell shape, and release of CK, manoalide attenuated none of them. In the Ca2+-free solution, LPC did not increase [Ca2+](i) with significantly less accu mulation of NEFA, but it changed the cell shape from rod to round and increased the release of CK. These results suggest that exogenous LPC increases the PLA(2) activity, which, however, may not be responsible for the LPC-induced damage in cardiomyocytes.