Injury-induced changes in cytosolic Ca2+ in individual rabbit proximal tubule cells

Cell injury was studied in cultured rabbit proximal tubular epithelial cells using digital-imaging fluorescent microscopy to relate changes in cytosolic Ca2+ ([Ca2+]i) to bleb formation and cell death. Fura-2-loaded cells were treated in normal (1.37 mM) and low (less than 5 microM) extracellular Ca2+ ([Ca2+]e) with 1) inhibitors of glycolysis (iodoacetate) and/or mitochondrial oxidation (KCN), 2) thiol-modifying reagents (N-ethylmaleimide, p-chloromercuribenzene, and p-chloromercuribenzene sulfonate), and 3) Ca2+ ionophore (ionomycin). All three types of injury produced both [Ca2+]e-independent and [Ca2+]e-dependent increases in [Ca2+]i. KCN + iodoacetate +/- [Ca2+]e did not produce blebbing or death within 60-90 min. Thiol modifiers and ionomycin produced blebbing, which correlated with sustained threefold or greater elevations of [Ca2+]i and loss of viability only after [Ca2+]i had risen severalfold. Blebbing and cell death could be prevented or delayed by treatment in low [Ca2+]e. Trypsin (x0.5) caused a transient (less than 5 min) elevation in [Ca2+]i as well as increases in intracellular Ca2+ pools.