Materials and Methods

A mitochondrial fraction was prepared from the livers of normal adult albino rats by the following procedure. The livers were quickly removed from rats killed by decapitation and homogenized in 5 volumes of ice-cold 0.25 M sucrose containing 0.001 M Versene, in a glass homogenizer of the Potter-Elvehjem type. Nuclei, debris, and whole cells were removed by centrifugation for 5 minutes at 500 X g at 0’. The mitochondrial fraction was then obtained by centrifugation at 18,000 X g for 20 minutes at O”, the high speed head of an International refrigerated centrifuge being used, and was washed twice with the sucrose-Versene solution, and finally suspended in sucrose-Versene or water just prior to use. Since it is now recognized that “mitochondria” prepared by conventional procedures of differential centrifugation may represent a range of cytoplasmic granules of varying chemical and biochemical properties (26, 27), this preparation will be described simply as rat liver particles.