Oxygen deprivation-induced injury to isolated rabbit kidney tubules.

The utility of freshly isolated suspensions of rabbit tubules enriched in proximal segments for studying the pathogenesis of oxygen deprivation-induced renal tubular cell injury was evaluated. Oxygenated control preparations exhibited very good stability of critical cell injury-related metabolic parameters including oxygen consumption, cell cation homeostasis, and adenine nucleotide metabolism for periods in excess of 2 h. Highly reproducible models of oxygen deprivation-induced injury and recovery were developed and alterations of injury-related metabolic parameters in these models were characterized in detail. When oxygen deprivation was produced under hypoxic conditions, tubules sustained widespread lethal cell injury and associated metabolic alterations within 15-30 min. However, when oxygen deprivation was produced under simulated ischemic conditions, tubules tolerated 30-60 min with only moderate amounts of lethal cell injury occurring, a situation similar to that seen with ischemia in vivo. Like ischemia in vivo, simulated ischemia in vitro was characterized by a fall in pH during oxygen deprivation. No such fall in pH occurred in the hypoxic model. To test whether this fall in pH could contribute to the protection seen during simulated ischemia in vitro, tubules were subjected to hypoxia at medium pHs ranging from 7.45 to 6.41. Striking protection from hypoxic injury was seen as pH was reduced with maximal protection occurring in tubules made hypoxic at pHs below 7.0. Measurements of injury-associated metabolic parameters suggested that the protective effect of reduced pH may be mediated by pH-induced alterations of tubule cell Ca++ metabolism. This study has, thus, defined and characterized in detail a new and extremely versatile model system for the study of oxygen deprivation-induced cell injury in the kidney and has established that pH alterations play a major role in modulating such injury.