[Mucosubstance and lectin histochemistry of DMH induced colonic tumor in rats]

Histo-pathological appearances of DMH-induced colonic tumor in Wistar rats were sequentially observed upto the 35th week after the drug administration. In our series, 28 tumors were successfully induced in the colonic mucosa of 19 out of 64 rats treated with DMH, and they were histologically diagnosed as adenocarcinoma. However, there were differences in the histo-pathological findings of the carcinoma between the distal colon and the proximal colon in rats. That is, the slowly growing type of well differentiated adenocarcinoma was likely to originate from the proper mucosa in the distal colon, while in the proximal colon the rapidly growing type of tumor did from atypical glands in the lymphoid follicles. Therefore, it was suggested that histogenesis and growing processes of the carcinoma were differed in the distal colon from that in the proximal colon in rats. Second, epithelial mucosubstances and lectin-binding properties of these lesions were examined histochemically. There were differences in the lectin-binding patterns of UEA-I and PNA between carcinomas and/or atypical glands in the lymphoid follicle and normal background mucosa in rat colon. In the UEA-I staining, almost all tumors were positively stained except for one case, and in the well differentiated type a positive staining was discernible at the cell apex and secretory product in tumors, while in the undifferentiated type, it was seen at the cytoplasma and secretory product. From these histopathological and histochemical studies it may be concluded that these lectins is likely to be useful as tumor markers for the large bowel, and also effective for a diagnosis of minute carcinoma in the large bowel.