Alteration to the permeability of plant and animal mitochondria submitted to Ca 2+ releasing agents

Abstract

1. 1. Mitochondria from different rat tissues and from plants were compared as regards their sensitivity towards Ca 2+ in the presence of different Ca 2+ releasing agents, and the phospholipase A 2 activity was evaluated in the different mitochondrial preparations. 2. 2. The mitochondria were exposed to Ca 2+ and an oxidant such as t -butylhydroperoxide or diamide or to Ca 2+ and inorganic phosphate, and plant mitochondria were seen to be much more resistant than liver, brain or kidney mitochondria of rats to the deleterious effects of these agents. 3. 3. The phospholipase A 2 activity is not directly involved in the alteration of the mitochondrial inner membrane permeability within the first 10 min of incubation under our experimental conditions. 4. 4. The protection conferred by ATP and Mg 2+ against Ca 2+ efflux from mitochondria or the decrease in the mitochondrial transmembrane electrical potential was also observed under our experimental conditions, but cannot be attribute to enhancement of the lysophospholipids resulting from the phospholipase A 2 activity.