Vinyl acetate induces intracellular acidification in mouse oral buccal epithelial cells

Vinyl acetate exposure in drinking water has been associated with tumor formation in the upper gastrointestinal tract of rats and mice. One potential mechanism for inducing carcinogenesis involves acidification of the intracellular environment due to the metabolism of vinyl acetate to acetic acid. Prolonged intracellular acidification is thought to produce cytotoxic and/or mitogenic responses that are the sentinel pharmacodynamic steps toward cancer. To determine whether exposure to vinyl acetate affects the intracellular pH of intact oral cavity tissue, isolated mouse oral buccal epithelium was loaded with the pH-sensitive dye BCECF, and then exposed to vinyl acetate concentrations ranging from 10 to 1000 microM for up to 4 min. Extracellular vinyl acetate exposure induced a progressive intracellular acidification that was reversible upon removal of the vinyl acetate. The rate of the acidification was concentration-dependent and increased exponentially within the concentration range tested. The magnitude of the vinyl acetate-induced acidification was inhibited by pretreatment with the carboxylesterase inhibitor bis(p-nitrophenyl)phosphate. These results are consistent with the hypothesis that vinyl acetate contributes to the generation and progression of oral cavity tumors via a process of intracellular acidification. Such a process has been proposed to have practical dose-response thresholds below which the intracellular environment can be maintained within homeostatic bounds and the contribution of exposure to carcinogenic risk is negligible.