Inactivation of Mitochondrial Permeability Transition Pore by Octylguanidine and Octylamine

Mitochondrial permeability transition occurs through a Ca2+-dependent opening of atransmembrane pore, whose identity has been attributed to that of the adenine nucleotide translocase(ANT). In this work, we induced permeability transition by adding 0.5 μM carboxyatractyloside.The process was evaluated analyzing Ca2+ efflux, a drop in transmembrane electric gradient,and swelling. We found that the amphiphyllic cations octylguanidine and octylamine, at theconcentration of 100 μM, inhibited, almost completely, nonspecific membrane permeability.Hexylguanidine, hexylamine, as well as guanidine chloride and hydroxylamine failed to doso. The inhibition was reversed after the addition of 40 mM Li+, Na+ K+,Rb+, or Cs+; K+ wasthe most effective. We propose that the positive charge of the amines interact with negativecharges of membrane proteins, more likely the ADP/ATP carrier, while the alkyl chain penetratesinto the hydrophobic milieu of the inner membrane, fixing the reagent.