Transplantable colonic adenocarcinomas in rats.

The induction of colonic adenocarcinoma using two different regimens of dimethylhydrazine (DMH) in Fischer F344 rats is described. Rats receiving 20 mg/kg of DMH per week for 20 weeks developed primary tumors with metastases, whereas rats receiving the same weekly dose for 15 weeks developed primary tumors only. The most common route of metastases was transcelomic which often was associated with ascites. The epithelial origin of malignant ascites cells was confirmed by immunofluorescent staining with antidesmosomal antibodies and demonstration of desmosomes by electron microscopy. When transplanted into syngeneic rats, the cells of the malignant ascites resulted in the development of adenocarcinomatous metastases.