5-Fluorouracil sensitive adenocarcinoma--a new experimental model in the rat.

Transplantable nitrosoguanidine-induced rat colonic carcinoma was transplanted into the liver of 49 rats in six different series during three years. Tumor growth in vivo was surveyed by repeated laparotomy at day eight and day seventeen, and 25 rats were treated with 5-fluorouracil (30 mg/kg body weight) once a day, between day 8 and day 17. Tumor take was one hundred per cent and the tumor growth rate was similar throughout the experimental period. No animals died due to treatment or due to progressive tumor growth. The animals treated with 5-fluorouracil revealed a 5 per cent weight loss compared to the controls but no other signs of health deterioration were observed. The tumors treated with 5-fluorouracil had a 70 per cent decrease of growth rate compared to control rats. Exposure of the tumor cells in vitro to 5-fluorouracil induced a dose--related decrease in surviving cells with a 50 per cent reduction of surviving cells 48 hours after exposure to 0.01 mg/ml of 5-fluorouracil. Thus, we present here a new, feasible and reproducible animal model, excellently suited to in vivo and in vitro studies of fluorinated pyrimidines and solid tumor growth.