Radiosensitivity and Biological Properties of Two Tumor Types Indigenous to the Same Host. VIII. Catalase Activity Within Three Intracellular Fractions and Its Response to Various Chemical Agents

Summary

The distribution of intracellular catalase activity of the mitochondrial, microsomal, and cell-sap fractions of the slower-growing epithelial, and the faster-growing spindle cell tumors, both indigenous to the same inbred strain of mice, was investigated. Livers from the same strain of mice were used as normal test material for controls. The catalase activity of the epithelial tumor was approximately 7 times greater than that of the faster-growing spindle cell tumor on a wet-weight basis. The catalase-specific activity of the epithelial-tumor mitochondrial fraction was approximately 5 times greater than that of the spindle cell tumor. The catalase activity of the combined fractions of the liver was 100 times greater than that of the epithelial tumor and 722 times greater than that of the spindle cell tumor on a wet-weight basis. The high percentage of catalase activity in the cell-sap fraction of the spindle cell tumor relative to that of the epithelial tumor is explained by the greater permeability or fragility of catalase-containing particles of the spindle cell tumor. Other indications of a difference in mitochondrial integrity of the two types of tumor are discussed. The response of catalase to pretreatment with 1.25 M sucrose, deoxycholate, and phosphate buffer at pH₂ was investigated for both tumors and the liver. The catalase of the mitochondrial fraction was increased about threefold, the cell-sap catalase was unaffected, and the microsomal catalase activity was slightly increased by pretreatment with the above chemical agents. The large increase in the catalase activity of the mitochondrial fraction is believed due to the release of this enzyme as a result of the injurious effects of these agents on the boundary membrane of the catalase-containing particle.