Induction of the non-selective mitochondrial pore in lymphoid cells. 1. Permeabilized rat thymocytes

The opening of the cyclosporin-sensitive pore in the inner membrane of mito chondria in rat thymocytes was studied. In thymocytes with digitonin-permea bilized plasma membrane, the mitochondrial pore was induced by Ca2+ overloa d, by uncoupling, by oxidation or cross-linking of membrane dithiols, and b y atractyloside, a specific inhibitor of the adenine nucleotide transporter . Pore opening was prevented by cyclosporin A (CsA) and by its non-immunosu ppressive analog MeVal-CsA. The sensitivity of the pore to CsA was decrease d by atractyloside and practically disappeared when it was added in combina tion with uncoupler. The main properties of the pore in mitochondria from t hymocytes and from hepatocytes are the same. Release of Ca2+ from thymocyte mitochondria induced by uncoupling is mediated by a specific uniporter and by the pore with similar rates.