Glutathione content and turnover in rat nasal epithelia

During inhalation exposure to airborne toxicants, the nasal epithelium may be subjected to local toxicity. Since glutathione (GSH) is often involved in xenobiotic metabolism, GSH status in these tissues has been examined. GSH content and apparent first-order rate constants for GSH turnover and synthesis were determined for respiratory epithelium covering the anterior ventral septum and naso and maxillo turbinates, olfactory epithelium covering the dorsal posterior septum, and olfactory epithelium of the dorsal meatus from male Fischer-344 rats. The three tissues had GSH concentrations that ranged from 2.9 to 4.2 mumol/g tissue as determined by the Ellman's assay and by HPLC equipped with an electrochemical detector. Animals were administered [35S]cysteine (Cys) by tail vein injection and rate constants for GSH turnover were estimated, after incorporation of Cys into tissue GSH pools, by the decrease in GSH-specific activity 1-102 hr after administration. Total [35S]GSH was analyzed by HPLC with a flowthrough radioactivity detector. The respiratory epithelium had an apparent biphasic rate of GSH turnover, with a rapid-phase half-life of 4.4 hr and a slow-phase half-life of 34 hr. The other epithelia had slower rates of GSH turnover, with half-lives greater than 30 hr. When half-lives of GSH turnover and GSH concentrations for nasal epithelia, and for 14 previously evaluated tissues, were compared it was found that tissues with high concentrations of GSH generally had a more rapid turnover of GSH than did tissues with low concentrations of GSH. However, apparent GSH turnover in the two regions of the olfactory epithelium poorly followed this trend.