Radiation-induced acute intestinal injury after abdominal irradiation is a common and serious problem. The aim of this study was to evaluate the protective effect of Lactobacillus delbrueckii subsp bulgaricus 133 on the activities of antioxidant enzymes such as glutathione reductase, glucose-6-phoshate dehydrogenase (G-6-PD), 6-phosphogluconate dehydrogenase glutathione-S-transferase (GST) after abdominal radiotherapy. Rats were administered L delbrueckii subsp bulgaricus 133, isolated from yoghurt, in a probiotic solution (2 mL) containing 10(10) CFU/mL by orogastric route using a feeding canula. Rats in group 1 (control) were not irradiated but received the probiotic solution. The remaining rats were subjected to a single dose of 11 Gy of gamma radiation to the abdominopelvic area and further divided into 2 groups. Group 2 received the probiotic and group 3 received a placebo for 7 days after irradiation. On day 8, rats were euthanized. Effects of the probiotic on the activities of the antioxidant enzymes were examined in segments of jejunum, ileum, and colon. Radiotherapy significantly increased the activity of the jejunum GST in group 3 (P = .038), but the GST activity in group 2 was similar to that in group 1. The G-6-PD activity showed a significant increase in jejunum of group 3 (P = .048) compared with the control group. The G-6-PD activity in the ileum was increased in both groups 2 and 3 compared with the control (P = .005). There was no difference in glutathione reductase and 6-phosphogluconate dehydrogenase activity in any of the intestinal segments between the groups. Although the pathogenesis of radiation enteritis is not clear, recent experimental studies suggest that the mechanism involves mucosal damage due to toxic oxygen radicals. These results support the idea that probiotics possess protective effects in radiation-induced intestinal injury possibly by preventing or limiting oxidative stress. (C) 2007 Elsevier Inc. All rights reserved.