Effect of γ-Irradiation on the Healing of Gastric Biopsy Sites in Monkeys

The acute effects of γ-irradiation on the gastric mucosa have been studied in a primate model. Fiberoptic gastroscopies were performed in 6 rhesus monkeys in the basal state as well as 3 h and 3, 7, and 9 days after total body irradiation (800 rads). Gastric biopsy specimens (diameter 1 mm) obtained during each session were examined using light microscopy and scanning electron microscopy; in addition, subsequent healing of the biopsy sites was assessed visually. Gastric biopsy sites were completely healed in 3 days in the basal state; in contrast, ulcer craters (diameter 1 mm) were still present at the site of the biopsies 3, 7, and 9 days after the biopsies were performed in irradiated animals. Light microscopic examination of the biopsy specimens demonstrated only lymphocytic infiltration of the lamina propria. In contrast, scanning electron microscopic examination revealed that the size and number of microvilli of the gastric surface epithelial cells were increased on the day of irradiation compared to basal; 3–9 days later, numerous gastric surface epithelial cells were damaged or had dissappeared so that bare areas of the lamina propria were visible in the specimens taken outside of the ulcer craters. These changes may reflect inadequate protection or insufficient regeneration of gastric mucosal cells which, in turn, would explain the persistence of ulcers after gastric biopsies were performed in irradiated monkeys.