RENAL MOUSE PROXIMAL TUBULAR CELLS ARE MORE SUSCEPTIBLE THAN MDCK CELLS TO CHEMICAL ANOXIA

To elucidate the mechanisms responsible for the resistance of continuous cell lines to anoxic injury, we have compared the effects of ATP depletion induced by chemical anoxia on primary cultures of mouse proximal tubular (MPT) cells and on Madin-Darby canine kidney (MDCK) cells. Inhibition of ATP production by cyanide and 2-deoxyglucose (CN + DOG) in the absence of dextrose reduced cell ATP content to <5% of control values in MPT cells and caused progressive deterioration in mitochondrial function as well as loss of cell viability in these cells. Cell free fatty acid (FFA) content rose from 4.3 +/- 0.9 to 23.7 +/- 2.0 mug/mg of total lipid weight after 4 h of CN + DOG (P < 0.05). The mitochondrial injury and cell death induced by CN + DOG in MPT cells was ameliorated by the addition of fatty acid-free bovine albumin to the cell medium, which reduced cell FFA content during chemical anoxia from 25.0 +/- 3.0 to 10.4 +/- 2.0 mug/mug (P < 0.05). The phospholipase A2 (PLA2) inhibitor, mepacrine, also resulted in functional protection and reduction of cell FFA content from 20.2 +/- 2.3 to 15.9 +/- 1.7 mug/mg (P < 0.05). These data suggest a role for phospholipase activation and accumulation of toxic lipid metabolites in the pathophysiology of MPT cell injury. We then compared cell injury induced by CN + DOG in MPT and MDCK cells. Despite comparable reduction in cell ATP content in the two cell types, injury was far more severe in MPT than MDCK cells. After 4 h of CN + DOG treatment, mitochondrial function was reduced to 20 +/- 2% of control in MPT compared with 64 +/- 4% of control in MDCK cells (P < 0.05). Similarly, cell viability was reduced to 22 +/- 2% after 4 h of anoxia in MPT cells but only to 72 +/- 3% in MDCK cells (P < 0.05). Chemical anoxia was also associated with a fourfold greater absolute increase in total FFA in MPT than in MDCK cells (19.4 +/- 2 vs. 5.4 +/- 1 mug/mg) (P < 0.05). In conclusion, factors independent of glycolytic adaptation contribute to the resistance of MDCK cells to anoxia. Our data suggest that the greater resistance of MDCK cells to injury compared with MPT cells is due, at least in part, to lesser FFA release. We hypothesize that differences in anoxia-induced PLA2 activity between the two cell types play a role in the resistance of MDCK cells to injury.