Rapid oxidation in vitro of endogenous and exogenous glutathione in bile of rats.

Biliary excretion of glutathione has recently been described but poorly characterized. Controversy has existed concerning the relative contribution of oxidized and reduced glutathione to total glutathione efflux from the liver into bile. We found that bile, unlike liver cytosol or buffer, had the unique ability to oxidize GSH rapidly (t 1/2 = 5 min) to the disulfide form by a nonenzymatic, O2, and pH-dependent chemical reaction inhibited by only certain chelating agents. Significant oxidation of GSH occurred during the collection of bile samples resulting in significant time-dependent alterations in the ratio of biliary GSH to GSSG. Thus the preponderance of GSSG in bile in the normal state reported by others represents a postexcretory in vitro artifact. Inhibition of oxidation by acidification of bile during its collection established the true contribution of GSH and GSSG to total biliary efflux.