Low-Level X-Radiation-Induced Vascular Alterations in Normal and DMBA-Treated, Tumor-Bearing Cheek Pouch Epithelium of Syrian Hamsters

Studies were conducted to examine late changes in vascular volume and vascular perfusion of normal and tumor-bearing Syrian hamster cheek pouches, treated either with DMBA, repeated low-level X radiation, or DMBA + X radiation. Hamsters received once-weekly 20-R exposures to the head and neck for 17 consecutive weeks. During weeks 1 to 5 and 7 to 11 of irradiation, 0.1% DMBA was applied to right cheek pouches twice weekly. Thirty-nine weeks after initial treatment, animals were injected intravenously with 51 Cr-labeled erythrocytes to determine cheek pouch blood volume and ^{86}{\rm RbCl}$ to determine the vascular perfusion of cheek pouch tissues. Following excision of tumors and pouches, 51 Cr and 86 Rb activities and histopathologic changes were assessed. Irradiated animals had no tumors, 53% of the DMBA-treated animals had tumors, and 75% of the DMBA + radiation-treated animals had tumors. Irradiated cheek pouches had increased blood volume, and DMBA-treated tumor-bearing pouches had increased blood volume and perfusion. DMBA + radiation-treated tumor-bearing pouches had increased blood volume similar to that seen in irradiated pouches and increased blood perfusion similar to that seen in DMBA-treated, tumor-bearing pouches. While the presence of DMBA-induced tumors was related to changes in vascular perfusion in all groups, low-level X radiation appeared to alter changes in blood volume caused by DMBA or DMBA-induced tumors.