Differences in the acute intestinal syndrome after partial and total abdominal irradiation in mice

The acute intestinal syndrome in mice was analysed after partial (PAI) and total abdominal irradiation (TAI). The LD50/15 was significantly higher after PAI (16.3 Gy) than after TAI (14.3 Gy). The dose-response curve for maximal weight loss also showed a shift of 1.8-2 Gy to higher doses after PAI compared with TAI. The X-ray survival curve for duodenal crypt cells was shifted by only 0.6 Gy for PAI and TAI. In order to assess the possible role of radiation-induced leucopenia and the influence of irradiating the spleen (shielded with PAI), lethality, weight loss and blood leucocyte counts were compared after PAI and TAI in splenectomized and non-splenectomized mice. No major difference in leucopenia was found between the different treatment groups, whereas the differences in lethality and weight loss between PAI and TAI remained the same. Shielding the spleen in the partial abdominal field therefore did not contribute to the difference in LD50/15. These findings imply that the increased LD50/15 after PAI compared with TAI was mainly due to shielding of a small part of the bowel (about 13 per cent of the abdominal area).