PATHOLOGICAL AND ENZYMATIC FEATURES OF 1,2-DIMETHYLHYDRAZINE INDUCED COLORECTAL CARCINOMAS IN RATS

Well- and moderately well-differentiated colorectal adenocarcinomas ac counted for 86% of all tumors induced by 1,2-dimethylhydrazine in rats , and were distributed throughout the colorectal tract. Poorly differe ntiated carcinomas, 14% of all tumors, were markedly restricted to the proximal half of colon, i.e., 94% of the poorly differentiated type w as found in the proximal colon and caecum. Thymidylate synthetase and thymidine kinase, key enzymes in the de novo and salvage pathways, res pectively, for pyrimidine nucleotide synthesis were found to be reduce d and elevated, respectively, with increasing cellular differentiation . These results suggest that biochemical differences in colorectal tum ors may be associated with differences in tumor frequency, distributio n, and histological type.