BIOCHEMICAL HETEROGENEITY OF THE CYTOPLASMIC PARTICLES ISOLATED FROM RAT LIVER HOMOGENATE

Abstract

By separating the cytoplasmic granules of 0.88 M sucrose homogenates of rat liver into eight fractions it has been possible to demonstrate marked chemical and enzymatic heterogeneity among the isolated microsomes and less pronounced heterogeneity among the isolated mitochondria. The more readily sedimented microsomes are rich in ribose nucleic acid and show high esterase, adenosine-5’-phosphatase, acid phosphatase and uricase activities, while the less readily sedimented microsomes, although rich in ribose nucleic acid esterase and adenosine-5’-phosphatase have low levels of acid phosphatase and uricase activities. The very small mitochondria differ from the larger ones in the levels of activities of all enzymes studied, with the exception of adenosine-5’-phosphatase; the most striking differences were found in the cases of acid phosphatase and uricase. A centrifugation schedule is given to isolate a "nuclear fraction," a mitochondrial fraction, a mixed fraction of smallest mitochondria and microsomes (of two types differing in optical density), a fraction of optically less dense microsomes, and a "supernatant fluid."