The intracellular distribution of glutathine (GSH) in cultured hepatocytes hasbeen investigated by using the compound monochlorobimane (BmCI) Approximately 10-20% of total cellular GSH in rat liver is sequestered in the mitochondrial matrix (6, 7). The size ofthis pool depends on cytosolic GSH synthesis (8) and the active transport of GSH into mitochondria via a multicomponent system recently described (9).Conventional cell-fractionation studies have not provided evidence for the existence of functionally distinct pools of GSH in hepatocytes other than those in the cytosol and mitochondria. Despite the known functions of GSH in DNA synthesis (10) and protection from oxidative DNA damage (11), little is known about the nuclear localization ofGSH and the factors regulating the nuclear GSH level. Tirmenstein and Reed (12), using fractionation and centrifugation techniques in nonaqueous medium, measured the nuclear GSH content in rat kidney and found values similar to those in the cytosol. Other fractionation techniques (such as selective permeabilization of cell constituents with various detergents) provided equivocal results (13,14). However, the latter investigations have suggested that a nuclear pool of GSH may exist in intact cells.Recent advances in image-analysis technology, together with the development of additional, nontoxic fluorescent indicators that can be used in intact cells, have facilitated an enormous input into the study of various aspects of cell physiology (15,16 ITo whom reprint requests should be addressed. 4412The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.

No abstract