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.

Alterations in CNS gene expression in a rodent model of moderate traumatic brain injury complicated by acute alcohol intoxication.

The combined effects of acute alcoholic intoxication and moderate traumatic brain injury (TBI) on zif/268, glial fibrillary acidic protein (GFAP), and preproenkephalin (PPE) mRNA expression were examined. Adult male Wistar rats received ip injections of a 5% alcohol solution (2.4 g/kg in a final volume of 20 ml isotonic saline) 10 min prior to fixed-head, mechanical injury. Using Northern analysis, a transient three- to fourfold induction of zif/268 mRNA levels was observed 45 min after injury in both TBI and alcohol-treated rats. This induction occurred in regions close to the impact site, namely, the olfactory bulb (OB) and frontal cortex (FTCTX) but not in the more distal piriform/amygdala cortex (P/A). No PPE mRNA changes were observed at 45 min for any experimental group. By 6 h, zif/268 transcript levels returned to or fell below basal levels in the OB and FTCTX while GFAP mRNA levels began to increase in TBI rats. At 24 h, GFAP mRNA levels were greatly increased in all three brain regions of TBI rats. However, alcohol inhibited the temporal induction of GFAP mRNA in the FTCTX and P/A triggered by TBI at 6 and 24 h. These results suggest that although acute alcohol intoxication prior to TBI does not influence gene expression patterns immediately after injury, it may minimize the transcriptional activation of astrocytes particularly in more distant brain regions that were influenced by the impact in nonintoxicated rats.