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Lysosomal Enzymes in Macrophages of Colonic Tumors Induced in Rats by 1,2-Dimethylhydrazine Dihydrochloride¹

Center of Experimental Pathology and Toxicology, Albany Medical College, Albany, New York 12208

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 ß-glucuronidase activity in macrophages in the stroma of these neoplasms. A dramatic increase in the number of acid phosphataserich 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.

¹ Supported by Research Grant 2-PO1-ES00226-10 from the National Institute of Environmental Health Sciences. Predoctoral fellowship from Hercules, Inc. awarded to T. A. B.

² Recipient of Research Career Development Award 1-K04-ES70608-05, partly supporting this work. To whom requests for reprints should be addressed.

Received 4/14/78. Accepted 6/ 1/78.