Conjugation of 1-naphthol in human gastric epithelial cells

The biotransformation of xenobiotics is essential to the maintenance of the body's integrity. Mucosal biotransformation has been well documented in the small and large intestine of animals and humans but whether the gastric mucosa plays a role in detoxifying ingested compounds remains largely unknown. The conjugation of the model phenolic compounds, 1-naphthol, by human gastric epithelial cells was assessed in vitro. Freshly isolated and cultured epithelial cells were prepared from surgical specimens obtained from patients undergoing total gastrectomy for cancer. Cell preparations were incubated with 1- 14C-naphthol over 1 hour and the glucuronide and sulphate conjugates formed were separated by thin-layer chromatography. Conjugation of 1-naphthol was observed with both freshly isolated and cultured cells. In freshly isolated cells, the 1 hour turnover of 1 microM 1-naphthol to its glucuronide and sulphate conjugates averaged 19% and 10% respectively. At higher 1-naphthol concentrations, both types of conjugate were formed at about the same rate, up to saturation (apparent Vmax = 0.07 nmol/mg protein/minute, and apparent Km = 40 microM). In cultured cells, the 1 hour turnover of 1 microM 1-naphthol to its glucuronide and sulphate conjugates averaged 35% and 8% respectively. These results suggest that the human gastric mucosa is a detoxifying organ, and that its role with regard to chemical carcinogenesis and drug first pass metabolism deserves further assessment.