Summary
The activity of alkaline and acid DNase and RNase was histochemically investigated in the rat liver during different stages of N-nitrosomorpholine-induced carcinogenesis.
The activity of acid and alkaline nucleases was considerably decreased in focal areas and later in the hyperplastic nodules, whereas the surrounding liver parenchyma demonstrated normal activity of these enzymes. Nuclease deficiency appeared at the 38th to 59th day of carcinogenesis. It preceded by approximately 56 to 75 days the morphological signs of cancer. In malignant hepatocellular tumors, nuclease activity was practically negative. In the necrobiotic cells of those malignant tumors, a reappearance of nuclease activity was observed, indicating that the deficient nuclease activity in cancer is not equivalent with the real diminution or disappearance of those enzymes but depends probably upon their binding with inhibitors.
It has been suggested that nucleases might be involved in the protection of genetic stability of normal cells against transforming nucleic acids.
Footnotes
- Received February 4, 1971.
- Accepted February 23, 1971.
- ©1971 American Association for Cancer Research.