[Cell kinetics of carcinoma originating from rat colitis induced by dextran sulphate sodium]

Forty male Wistar rats were given 1% dextran sulphate sodium (M.W.: 50,000) as drinking water for six months. Well-defined elevated lesions were apparent in 12 (30%), showing the histological features of well differentiated adenocarcinoma. Focal atypical glands were histologically observed in 16 (40%). In vivo labeling of bromodeoxyuridine (BrdU) showed significant differences in S-phase cells among cancer (27.0 +/- 2.4%, atypical glands (20.8 +/- 5.9), regenerative mucosa (14.4 +/- 4.4) and normal mucosa (7.7 +/- 2.6), respectively (p < 0.01). BrdU labeling index of the upper part of the mucosal layer was smaller than that of the lower part in atypical glands, regenerative mucosa or normal mucosa, but they were similar in cancer. DNA aneuploidy was not detected either in cancer or in regenerative mucosa by flow cytometry. Ames test proved the low mutagenic potency of 1% DSS (Ames ratio, 2.1). In this experiment, colonic carcinoma seems to originate from mucosal inflammation itself.