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Alterations in Ribonuclease Activities in the Plasma, Spleen, and Thymus of Tumor-bearing Mice

Section of Immunology and Cell Biology [W. P. D., L. P. K., M. R. R.], and Section of Enzymology and Drug Metabolism [C. C. L.], NIH, National Cancer Institute, Baltimore Cancer Research Center, Baltimore, Maryland 21211

Six transplantable murine tumor models were evaluated for changes in RNase activity. This study was conducted with spleen and thymus homogenates, as well as with plasma collected from tumor-bearing mice. Nuclease activity directed against the synthetic substrates, polyadenylic acid, polyuridylic acid, and polycytidylic acid, was measured and the data obtained for tumor-bearing animals were compared to their normal counterparts. Elevated activity against polyuridylic acid was observed in the plasma of all tumor-bearing mice. Although not as all inclusive, RNase levels in both the spleen and thymus were generally altered as well. The observance of unilateral changes in nuclease activity directed against the synthetic substrates demonstrated that, in most cases, two or more enzymes were being detected. The assay may have some eventual value in the monitoring of cancer.

¹ To whom requests for reprints should be addressed, at Baltimore Cancer Research Center, 3100 Wyman Park Drive, Baltimore, Md. 21211.

Received 5/28/74. Accepted 10/16/74.