Transport and action of spermine in rat heart mitochondria.

ABSTRACT

At concentrations of 0.5-1.0 mM, spermine fully prevents the fall of membrane potential induced in rat heart mitochondria either by aging at room temperature or by the addition of palmitoyl CoA. Spermine also prevents the inhibitory action of palmitoyl CoA on adenylate translocase activity. When added to heart mitochondria de-energized by the same damaging conditions (aging or addition of palmitoyl CoA) spermine restores both membrane potential (provided that ATP is also added) and the activity of adenylate translocase. A part of added spermine is immediately bound to anionic sites on mitochondrial membranes, another part is slowly transported into heart mitochondria. Whereas binding is an energy independent process, transport is driven by the transmembrane potential. Spermine penetrates the mitochondrial matrix at significant rates only at high membrane potential, such as that produced either by phosphate transport or addition of nigericin.