New technique to assess hypoxia-induced cell injury in individual isolated renal tubules

Freshly isolated renal proximal tubules are a valuable model to study mechanisms of cell injury induced by hypoxia [1], The extent of cell injury has previously been quantified by determining the release of lactate dehydrogenase (LDH) and by measuring cellular adenosine triphosphate (ATP) and potassium (K) in suspensions of tubules [1, 21. However, the cellular pattern of hypoxic tubule injury is known to be heterogeneous and differences in cellular damage between tubules, as well as within individual tubules, have been described [1]. The present methods for quantification of cell injury as well as spectofluorometric measurements of intracellular ion concentrations with ion sensitive dyes (such as for Ca2, Na, H, Mg2) provide data which represent averages from all tubules in the suspension. Hence, using tubules in suspension prohibits correlation of cytoplasmic ion changes with cellular injury occurring in individual tubules or cells over time. This limitation of studies using tubular suspensions led us to develop a method for induction of hypoxic injury and assessment of cell injury in individual tubules and individual tubular cells.