On the opening of an insensitive cyclosporin A non-specific pore by phenylarsine plus mersalyl.

The purpose of this work was addressed to provide new information on the effect of thiol reagents on mitochondrial non-specific pore opening, and its response to cyclosporin A (CSA). To meet this proposal phenylarsine oxide (PHA) and mersalyl were employed as tools to induce permeability transition and CSA to inhibit it. PHA-induced mitochondrial dysfunction, characterized by Ca2+ efflux, swelling, and membrane de-energization, was inhibited by N-ethylmaleimide and CSA. Conversely, mersalyl failed to inhibit the inducing effect of phenylarsine oxide, it rather strengthened it. In addition, the effect of mersalyl was associated with cross-linking of membrane proteins. The content of membrane thiol groups accessible to react with PHA, mersalyl, and PHA plus mersalyl was determined. In all situations, permeability transition was accompanied by a significant decrease in the whole free membrane thiol content. Interestingly, it is also shown that mersalyl hinders the protective effect of cyclosporin A on PHA-induced matrix Ca2+ efflux.