An electron and fluorescence microscopic study of LLC-PK1 cells, a kidney epithelial cell line: normal morphology and cyclosporin A- and cremophor-induced alterations

The present study demonstrates the following: (I) At high concentrations cyclosporin A is toxic to LLC-PK1 cells and at intermediate concentrations also alters intracellular morphology in this same system. Even though these cells differ morphologically from renal cortex in a number of ways, the morphological changes in this system caused by cyclosporin A resembled in certain respects its reported morphological effects in vivo. Thus, LLC-PK1 cells may provide a suitable system for investigating certain aspects of the nephrotoxicity of cyclosporin A and its underlying mechanism. (2) The cytotoxic effects of cyclosporin A on LLC-PK1 cells demonstrated a relatively distinct threshold concentration, suggesting that a threshold for in-vivo nephrotoxicity might also exist. (3) Cremophor, an oil used clinically as the vehicle for cyclosporin A, was also found to be cytotoxic towards LLC-PK1 cells at high concentrations, as well as to alter the morphology of these cells at lower concentrations. This finding supports previous suggestions that cremophor itself may have a nephrotoxic effect. (4) Finally, we have found that Nile red can be used as a fluorescent probe for the rapid and simple detection of drug-induced, lipid-rich structures in cell cultures. In addition to its use in experimental systems, Nile red might also be employed to examine biopsy material and/or to look for the occurrence of lipid-rich structures (released from disrupted cells of, e.g. the renal cortex) in urine.