Biochemical and Osmotic Properties of Skeletal Muscle Mitochondria

Abstract

IN earlier investigations¹ we found that pigeon breast-muscle mitochondria isolated in 0.25 M sucrose possessed many of the properties exhibited by liver mitochondria, but lacked those features which are usually associated with fresh preparations of the latter. Such features include the so-called latent adenosinetriphosphatase (ATPase) activity², and high P : O ratios when oxidizing α-ketoglutarate. The incorporation of 0.001 M ethylenediaminetetra-acetate in the 0.25 M sucrose, first suggested to us by Dr. A. L. Lehninger³, and also used with beneficial effects by Slater and Cleland⁴ for the preparation of heart-muscle mitochondria, brought about considerable improvement in our preparations from pigeon breast muscle. When fresh, these mitochondria possessed latent ATPase activity and with α-keto-glutarate P : O ratios greater than 2 were obtained, but on storing at 0°, swelling could be observed and the mitochondrial ATPase activity increased progressively until finally after 3 hours it was no longer activated by 2 : 4 dinitrophenol (DNP).