Impurity in RNA Preparations which Inactivates RNase Inhibitor and Increases Alkaline RNase Activity. ∗

Summary

Preparations of commercial ribonucleic acid have been shown to contain a contaminating substance which interferes with assay of pancreatic ribonuclease, intracellular ribonuclease activity, and activity of the endogenous ribonuclease inhibitor. The impurity is probably a metal since its action is annulled by dialyzing the nucleic acid against Versene or by adding Versene to the assay system. The presence of the impurity results in inactivation of the endogenous ribonuclease inhibitor of the tissues examined (liver, adipose tissue, spleen) which causes the release in active form of the inactive alkaline ribonuclease of the supernatant fluid fractions and also removes the inhibition of the particulate alkaline ribonuclease. This in turn, leads to high alkaline ribonuclease activities and high alkaline/acid ribonuclease ratios in homogenates of the tissues. The results emphasize the importance of the purity of the ribonucleic acid substrate in making accurate assays, under certain conditions, for the levels of intracellular acid and alkaline ribonuclease, pancreatic ribonuclease, and ribonuclease inhibitor and may explain some previous discrepant reports of these measurements.