CHANGES IN FUNCTIONAL VASCULARITY AND CELL NUMBER FOLLOWING X-IRRADIATION OF A MURINE CARCINOMA

Post-irradiation changes in vascular function and cell number in the transplantable SCL [mammary] carcinoma of A/J mice were examined. Vascular volume per g tumor, as measured by 51Cr-labeled red blood cell dilution, increased within 1 day after 1000 or 2000 rad and then decreased. The number of living cells per g tumor, estimated from single-cell preparations, declined to a minimum at day 3 post-irradiation with 1000 or 2000 rad. Calculation of vascularity on a per living cell basis indicated that the vascular volume increased to 197% and 286% of controls 3 days after irradiation with 1000 and 2000 rad, respectively. Post-irradiation reoxygenation of hypoxic tumor cells may be caused by a decrease in O2 consuming cells which is greater in magnitude than the corresponding decrease in functional vascularity. [Tumor radiotherapy is discussed.].