Lysosomal enzymes in macrophages of colonic tumors induced in rats by 1,2-dimethylhydrazine dihydrochloride.

Ten weekly doses of dimethylhydrazine (30 mg/kg) were given to rats to induce colonic tumors. Histochemical and electron cytochemical studies revealed a distinct pattern of lysosomal acid phosphatase and beta-glucuronidase activity in macrophages in the stroma of these neoplasms. A dramatic increase in the number of acid phosphatase-rich macrophages was present in adenomas when compared to that in normal colonic mucosa. Fewer numbers of these cells were seen in well-differentiated adenocarcinomas, and they were barely detectable in highly invasive mucinous adenocarcinomas. It is postulated that these macrophages may play a role in preventing the invasion of adenomatous neoplasms into the submucosa. Application of histochemical techniques to study macrophage lysosomal enzymes may prove a useful diagnostic tool in differentiation of human colonic tumors for prognostic evaluation.