Swelling in Bean Shoot Mitochondria Induced by a Series of Potassium Salts of Organic Anions

A series of potassium salts of organic anions were examined for their effect on the volume change of bean shoot mitochondria as measured by spectrophotometric light scatterings. A passive osmotic swelling (substrate independent) as well as an active osmotic swelling (substrate dependent) was shown with a series of organic anions. Both oxidizable substrates and non-oxidizable substrates induce swelling. The monocarboxylic acids including acetate, β-OH-butyrate, propionate, and pyruvate induce active swelling which is partially inhibited by the presence of an ATP generating system or the uncoupler 2,4-dinitrophenol (DNP). Dicarboxylic acids produce less extensive rates and amounts of active swelling. Moreover, the swelling induced by dicarboxylic acids is inhibited less completely by an ATP generating system or by DNP. Metabolizable substrates including citrate, pyruvate, glutarate, and α-oxo-glutarate induced swelling despite their poor rates or lack of oxidation. It was concluded that with these anions, penetration across the inner membrane as measured by osmotic swelling of isolated mitochondria is not the rate limiting step in their metabolism.