Histological features and genetic changes induced by X-rays in intestinal metaplasia (IM) in rats were assessed by histochemistry and immunohistochemistry. A time course study and a PCR-SSCP analysis were performed. The IMs in rats were classified into two major types according to the cells forming the metaplastic glands. The first (the GI type) had both gastric and intestinal type cells forming the metaplastic glands. The second (the I-sol type) had solely intestinal cells forming the metaplastic glands. This characterization is similar to that used to define human IMs. The occurrence of IMs of the I-sol and GI types in rats gradually increased with time after X-ray irradiation. The number of IMs of the GI type was relatively high at 2 and 4 weeks after X-ray irradiation, and was low thereafter. On the other hand, the number of IMs of the I-sol type was extremely low at 2 weeks after treatment, then increased with time, and reached a maximum at 77 weeks after treatment. In the PCR-SSCP analysis, there were no alterations of the H-ras, Kras, and p53 genes in the IM glands of rats treated with X-ray irradiation 8 weeks earlier. These observations suggest that the phenotypic change from IMs of the GI type to the I-sol type occurred without ras and p53 gene alterations.
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