Differential Effect of Ionizing Radiation on Mammary Tumor Virus Activity Associated With Blood Cells and Mammary Tumor Cells

Abstract

Studied were the effects of different doses of X-rays and γ-rays on mammary tumor virus (MTV) activity associated with blood, bone marrow, and mammary tumor cells. Irradiation with doses as high as 5000 and 10,000 rads had no adverse effect on MTV activity associated with mammary tumor cells or cell-free extracts of mammary tumors. In contrast, MTV activity associated with blood or with bone-marrow cell colonies in spleen (BMCCS) was inactivated at radiation dose levels of ≥ 1100 rads. The inactivation of BMCCS, or blood cell-associated MTV, could not be accounted for by a delay in its appearance in the peripheral circulation, nor were the results affected by the use of test mice with highly stimulated mammary glands for the MTV assay. These results provide a simple method for selective destruction of MTV activity associated with blood cells and suggest that cell division might be a prerequisite for the expression of the MTV activity in these cells.