The contribution of endogenous polyamines to the permeability transition of rat liver mitochondria

Abstract

Spermine and spermidine are present in rat liver mitochondria at the concentrations of 3.5 and 1.8 nanomoles/mg protein, respectively. Addition of 50 microM Ca2+ and 1 mM Pi to respiring mitochondria induces, concomitantly with mitochondrial swelling and Mg2+ efflux, a consistent release of polyamines, which is either prevented by cyclosporin A or Mg2+. Addition of 0.1 mM spermine to mitochondria deenergized by Ca2+ and phosphate restores, like 1 mM Mg2+, transmembrane potential at the physiological level, while either cyclosporin A or ADP are ineffective. The presence of polyamines in the matrix space should be considered relevant, like Mg2+, in controlling the permeability transition of liver mitochondria.