CA2+-TRIGGERED MEMBRANE-PERMEABILITY TRANSITION IN DEENERGIZED MITOCHONDRIA FROM RAT-LIVER

The opening of the cyclosporin A-sensitive permeability transition pore (MTP) in deenergized mitochondria was induced only at millimolar Ca2+. Pretreatment of the mitochondria with 'inducers', such as duroquinone and phenylarsine oxide, allowed observing the pore opening at 0.01-0.1 mM Ca2+. Duroquinone caused a rapid (within 20 s) NAD(P)H oxidation which was followed by a slow (20 min) induction of the pore sensitive to low Ca2+. Phenylarsine oxide capable of cross-linking of vicinal SH-groups caused pore formation without the oxidation of NAD(P)H. The pore opening by both 'inducers' was prevented by N-ethylmaieimide. We propose that oxidation or cross-linking of critical dithiol(s) in membrane proteins increase the sensitivity of a putative 'Ca2+-sensor' that regulates the permeability transition pore opening.