Pancreatic acinar cell tumors in rats induced by 3,2'-dimethyl-4-aminobiphenyl.

Pancreatic acinar cell lesions, including foci, nodules, adenomas and in situ carcinomas, were found in male F344 rats given s.c. injections of 3,2'-dimethyl-4-aminobiphenyl (DMAB) at doses ranging from 50 to 167 mg/kg body weight in two 60-week experiments. The pancreatic lesions induced by DMAB were essentially the same as those reported in rats treated with 4-hydroxyaminoquinoline-1-oxide and azaserine. DMAB at high doses induced pancreas acinar cell as well as fat necrosis, and tumorigenicity for the pancreas was most effective at high necrogenic levels of carcinogen exposure. Mean labeling indices in basophilic foci, acidophilic foci, nodules and adenomas assessed by bromodeoxyuridine incorporation were elevated to approximately 0.69, approximately 2.17, approximately 1.43 and approximately 0.96% respectively, in contrast to the value of 0.39% observed for the surrounding normal acinar cells. The increase was significant in the acidophilic foci and nodules and the fact that these lesions had very high labeling indices suggests that they may have potential for progression to tumors.