Nephrotoxicity in vitro: Role of ion deregulation in signal transduction following injury—Studies utilizing digital imaging fluorescence microscopy

Abstract

Over the years, many approaches have been utilized for studying in vitro toxicity in the kidney. These have included the use of isolated perfused kidneys, renal slices, isolated nephron explants and cultured tubular epithelium. Currently, in vitro systems of either primary cultures or cell lines make it possible to use newly developed fluorescent probes and digital imaging fluorescence microscopy coupled with image analysis to quantify various ions (e.g. [Ca 2+] i, [Mg 2+] i, [Na +] i and [H +] i) in individual live cells. Methods have been developed for the primary culture of rat, rabbit and human proximal tubular epithelium and these cultures are being utilized for the study of acute cell injury and for the comparison of animal cell data with that of human cells. In the current studies, the fluorescent probe, Fura 2, was used to observe changes in [Ca 2+] i as they relate to cell injury. The results show that changes in [Ca 2+] i begin very early after treatments with a variety of agents that produce lethal and sublethal toxic injuries. These injuries can increase [Ca 2+] i from its normal 100 n m level to a 2 μ m level. The rise in [Ca 2+] i precedes early bleb formation and cell death. Elevated [Ca 2+] i may also activate enzymes such as lipases and proteases that lead to cell death.