Ribonuclease Activity in Some Transplantable Rat Hepatomas.

Several parameters of ribonuclease activity have been determined in a series of transplantable rat tumors and liver from the host rats. These include ribonuclease inhibitor activity, pH activity curves, and the distribution and specific activity of acid and alkaline ribonuclease in subcellular fractions. For those hepatomas studied, compared with liver from the tumor-bearing animal, the following changes were observed: ribonuclease inhibitor in all hepatomas was lower (two exceptions); the percentage of acid and alkaline ribonuclease in the mitochondrial fraction was greatly lowered; the percentage of acid or alkaline ribonuclease in the nuclear fraction was either unchanged or elevated; the percentage of alkaline ribonuclease in the microsomal fraction was nearly doubled, and this was accompanied by a large increase in specific enzyme activity; and acid ribonuclease was considerably increased in the supernatant fraction. Many other changes were found but they were not observed in all the tumors.