Inactivation of mitochondrial permeability transition pore by octylguanidine and octylamine

Mitochondrial permeability transition occurs through a Ca2+-dependent openi ng of a transmembrane pore, whose identity has been attributed to that of t he adenine nucleotide translocase (ANT). In this work, we induced permeabil ity transition by adding 0.5 mu M carboxyatractyloside. The process was eva luated analyzing Ca2+ efflux, a drop in transmembrane electric gradient, an d swelling. We found that the amphiphyllic cations octylguanidine and octyl amine, at the concentration of 100 mu M, inhibited, almost completely, nons pecific membrane permeability. Hexylguanidine, hexylamine, as well as guani dine chloride and hydroxylamine failed to do so. The inhibition was reverse d after the addition of 40 mM Li+, Na+ K+, Rb+, or Cs+; K+ was the most eff ective. We propose that the positive charge of the amines interact with neg ative charges of membrane proteins, more likely the ADP/ATP carrier, while the alkyl chain penetrates into the hydrophobic milieu of the inner membran e, fixing the reagent.