[Stimulating effects of 3% acetic acid on the induction of esophageal tumors in rats].

The probe--mediated intragastric injection of 50 mg/kg ethyl ether of N-nitrososarcosine (EENS) 5 times a week for 6 months was followed by the development of multiple tumors in 91.8% of 120 noninbred male rats supplied by a local animal farm: esophagus--85.7%, fore-stomach--73.4% and throat--22.4%. The lesions in the esophagus and the fore-stomach entry were similarly frequent (61.2-75.5%) which was matched by a much lower incidence rate (22.4%) for the remaining parts of the fore-stomach. The combined intragastric injection of 3% acetic acid (0.5 ml thrice a week) for 8 months and EENS for 6 months boosted the total frequency of neoplasms to 100% and resulted in increased multiplicity of tumor--from 9.8--10.7 for EENS alone to 14.5 for EENS + acetic acid. Most lesions occurred in the fore-stomach entry as far as the level of tumor (squamous cell carcinoma and papilloma) development, frequency and relative risk (number of tumors. v. actual number of animals) are concerned. A long--term treatment with 3% acetic acid alone was followed by chronic inflammation of the esophageal mucosa rather than tumor development.