CHARACTERISTICS OF REVERSIBLE AND IRREVERSIBLE CA2-INDUCED CA2+ RELEASE FROM MITOCHONDRIA OF PERMEABILIZED EHRLICH ASCITES TUMOR-CELLS()

The cyclosporin A-sensitive high permeability state of the mitochondri al inner membrane in Ehrlich ascites tumor cells has been investigated . Ca2+ is shown to induce both self-reversible and irreversible transi tions of the mitochondrial inner membrane in the state of high permeab ility. Addition of ADP effectively suppresses the reversible transitio n but has no effect on the irreversible one. Bromophenacyl bromide, an inhibitor of phospholipase A(2), effectively inhibits both the revers ible and irreversible permeability transitions. During the development of nonspecific permeability the accumulation of both lysophosphatidyl choline and lysophosphatidylethanolamine has been found to occur in Eh rlich ascites tumor cell mitochondria. It is proposed that products of phospholipid hydrolysis are involved in the formation of the nonselec tive pore in the inner mitochondrial membrane during the induction of nonspecific conductivity.