STRAIN DIFFERENCES IN THE INDUCTION OF INTESTINAL METAPLASIA BY X-IRRADIATION IN RATS

Strain differences in the susceptibility of rats to induction of intes tinal metaplasia by X-irradiation were examined. The gastric regions o f 5-week-old males of five inbred strains of rats (F344/NSlc, Copenhag en, Buffalo/NacJcl, and ACI/NHos) and three strains of randomly bred r ats (HOS:Donryu, Slc:Wistar, Slc:SD) were irradiated with a total dose of 20 Gy X-ray given in two equal fractions at 3-day intervals. When examined after the rats were killed, 6 months after the last irradiati on, the number of intestinal metaplastic crypts positive for alkaline phosphatase (ALP) was highest in the Donryu and lowest in the Copenhag en rats. Morphologically, the number of crypts with intestinal metapla sia in the glandular stomachs of Donryu, Wistar, SD, and Buffalo rats was higher than the number in ACI, F344, and Copenhagen rats. Intestin al metaplasia was more frequently observed in the pyloric than in the fundic glands. These results demonstrate that the induction of intesti nal metaplasia by X-irradiation in rats is greatly influenced by the r at strain.