A new experimental model to study preneoplastic lesions in achalasia of the esophagus.

PURPOSE Develop an experimental model to study esophageal preneoplastic lesions induced by diethylnitrosamine in rats with achalasia. METHODS Male Wistar rats were divided into four groups: control--C (n=8); rats with megaesophagus--B (n=8); rats treated with DEN--D (n=15) and rats with megaesophagus plus DEN--BD (n=15). Megaesophagus can be experimentally obtained in rats by topical application of benzalkonium chloride. The morphology and PCNA labeling index of the epithelium were evaluated. RESULTS The morphometric analysis showed an increase in epithelial thickness in the animals of group BD (2166+/-1012 mm2) when compared to the other groups (C = 878+/-278 mm2; B = 1746+/-144 mm2 and D = 1691+/-697 mm2), mainly due to basal layer hyperplasia, besides an increase in the keratin of the superficial layer. The PCNA labeling index in the basal layer was significantly higher in the group BD (0.695+/-0.111) when compared to the other groups (C = 0.490+/-0.132; B = 0.512+/-0.215 and D = 0.477+/-0.198). CONCLUSIONS Our data confirm in an experimental model the previous observation in humans of increased epithelial cell proliferation during the esophageal carcinogenic process in achalasia and may be useful to further studies on the mechanisms of the esophageal carcinogenesis and the the design of follow-up endoscopic studies for patients with achalasia.