Cellular and subcellular heterogeneity of glutathione metabolism and transport in rat kidney cells

Selective permeabilization of plasma membranes with digitonin produced separation of cytosolic and mitochondrial compartments of proximal tubular (PT) and distal tubular (DT) cells from a rat kidney. Subcellular distributions of several intracellular glutathione (GSH)-dependent enzymes were similar in the two cell types but specific activities were significantly higher in PT cells, indicating that DT cells, particularly in their mitochondrial fraction, have a diminished capacity to detoxify reactive oxygen species. To enable isolation of suspensions of mitochondria, renal cells were treated with digitonin followed by the bacterial protease nagarse and were filtered through polycarbonate membranes. Activity distributions of enzymatic markers for subcellular fractions were quantitated and uptake of GSH was studied in suspensions of PT and DT cell mitochondria. While PT cell mitochondria catalyzed rapid uptake of GSH that was inhibited by malate, indicating involvement of dicarboxylate carriers, DT cell mitochondria exhibited limited capacity for GSH uptake that was not inhibited by substrates for the two dicarboxylate carriers. This report provides the first description of methodology for the preparation of mitochondria from renal cells derived from specific nephron cell types and shows that mitochondria from DT cells have a significantly lower capacity to use GSH for detoxification and regulation of redox status. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.