The effect of radiation alone and of radiation followed by hyperthermia on the vasculature of mouse intestine.

The effect on the vasculature of mouse intestine was observed following: (a) irradiation alone; and (b) irradiation followed at intervals of 0-60 days by hyperthermia. Specimens of intestine were removed after sacrifice and the vasculature revealed by benzidine staining before clearing in resin. The mean visible venous tree (VVT) was used as a parameter for assessing damage. The same hyperthermal treatment was used throughout: 1 h at 41.0 degrees C with the gut externalised. Following irradiation by 9 Gy, the VVT was not significantly reduced in the first 15 days, but decreased steadily by 34% in the next 45 days. In addition two transient reversible reductions occurred: the first immediately following irradiation, not counteracted by hyperthermia and thought to result from spasm; the second after about 40 days, counteracted by heating and thought to be caused by partial occlusion of the arterioles, resulting from irradiation. Reduction in VVT 26 days after irradiation appeared to be independent of dose from 6 to 10 Gy. Sensitivity to hyperthermia was maximal 15 days after irradiation.