Renal Blood Flow, Glomerular Filtration Rate, and Renal Morphology in Cyclosporine-Induced Acute Renal Failure in Munich-Wistar Rats

The mechanism of clinical cyclosporine nephrotoxicity has remained unclear. We have established an animal model of cyclosporine-induced acute renal failure in the male Munich-Wistar rat by giving four daily doses of parenteral cyclosporine 60 mg/kg intraperitoneally (IP). In this model, 20 minutes of bilateral renal ischemia preceding the first cyclosporine dose did not significantly increase the renal failure, but did increase mortality (65% v 17%), which was due in part to the CNS effect of cyclosporine. Pair-fed and pair-watered vehicle and saline controls were used. The renal morphologic changes induced by the castor oil vehicle of the commercial parenteral cyclosporine solution were quantitatively similar to those induced by cyclosporine, although the severity of the changes by light microscopy was considerably less in the vehicle-treated groups. However, by electron microscopy, pale lipid vacuoles were seen only in the cyclosporine-treated groups, whereas dense alterations in lysosomes and dilated endoplasmic reticulum were also seen in other groups. Renal blood flow determined by electromagnetic flow probe showed a significant decline during 2 hours after a single IP injection of cyclosporine (6.6 ± 0.4 to 5.0 ± 0.6 mL/min). A similar decline was seen following injection of the castor oil vehicle of the commercial cyclosporine parenteral preparation (6.6 ± 0.5 to 5.1 ± 0.5 mL/min), but not after an injection of a similar volume of mineral oil (6.7 ± 0.3 to 6.3 ± 0.2 mL/min). These studies suggest that brief renal ischemia does not increase cyclosporine nephrotoxicity significantly in this rat model. Reproducible renal failure can be induced by four daily IP injections of cyclosporine alone in a dose of 60 mg/kg, but in this model, the initial decrease in the blood flow and all tubular histologic changes except pale lipid vacuoles can be induced by the castor oil vehicle.