ENHANCEMENT BY PEPTIDE HISTIDINE ISOLEUCINE OF EXPERIMENTAL CARCINOGENESIS IN THE COLON OF RATS INDUCED BY AZOXYMETHANE

The effects of peptide histidine isoleucine (PHI) on the incidence and histology of colon tumors induced by azoxymethane (AOM), and on the l abeling index of colon mucosa were investigated in Wistar rats. Rats r eceived weekly s.c. injections of 7.4 mg/kg body weight of AOM for 10 weeks, and of 1.0 or 4.0 nmol/kg body weight of Pi-II until the end of the experiment in week 35. Administration of PHI at the higher, but n ot the lower dosage, significantly increased the incidence of colon tu mors. PHI had no influence on the histology of colon tumors or adenoca rcinomas. It also caused significant increase in the labeling index of colon epithelial cells. These findings indicate that PHI enhances col on carcinogenesis, and that its effect may be related to increasing pr oliferation of colon epithelial cells.