Effect of polycation peptides on mitochondrial permeability transition.

Synthetic polycation peptides obtained with the basic aminoacids lysine, arginine and ornithine are able to inhibit the permeability transition induced in mitochondria by calcium ions and inorganic phosphate. At least three basic aminoacid residues must be present in the peptide in order to elicit the inhibitory effect. In the presence of synthetic polycations and similarly to spermine, a lack of correlation between inhibition of swelling and glutathione release is apparent, since glutathione release occurs before the onset of a large amplitude swelling. The same lack of correlation is observed in the presence of cyclosporin. From the results obtained with the above reported polycations, different in both aminoacid composition and length, it appears that the effect is not to be referred to the individual properties of the molecules examined but rather to their cationic character; in addition, a critical number of positive charges is necessary to elicit the effect.