Abstract
X-ray induction of tumors were examined in five-week-old male CD(SD) : Crj rats, treated with two 10 Gy doses to the gastric region with a 3-day interval (total 20 Gy). After irradiation, the rats received a 1% NaCI supplement in the diet and survivors were killed 22 months after the first X-irradiation. The total tumor incidence was 59% (48 of 82 effected rats), the first animal demonstrating a sarcoma at day 273. Islet tumors of the pancreas appeared from the 455 day time point. Pancreatic and kidney tumors developed in 15 rats (18%) each, and apocrine tumors at the irradiated site and sarcomas in 9 rats (11%) and 5 (6%), respectively. Gastric tumors were found in 3 rats (4%). Immunohistochemistry revealed the islet tumor cells to be generally positive for insulin, although some cells contained somatostatin or glucagon, but not gastrin. The present results thus showed that the insulinomas and tumors other than gastric lesions are induced by X-irradiation of the upper peritoneal region.
