AN IN VITRO MODEL FOR ANALYZING THE NEPHROTOXICITY OF CYCLOSPORINE AND PRESERVATION INJURY

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Abstract
Renal damage caused by cyclosporine (CsA) has been documented. Clinical experiences have shown preservation injury further potentiates CsA nephrotoxicity. This study examined the mechanism of nephrotoxicity defined by changes in protein synthesis, DNA synthesis, and ornithine decarboxylase activity in an in vitro model. Initial results showed that CsA inhibited dog kidney epithelium cell (MDCK) replication at a dose of 200 ng after 24 hr (P < .01) and 100 ng after 48 hr (P < .01). Protein synthesis was inhibited with 100 ng after 24 and 48 hr (P < .01). There was a reduction in ODC activity with 200 ng CsA (P < .05). Methods for simulating transplant-related injuries were then developed. Under ischemic conditions, 18 hr were required before a synergistic effect with CsA produced a reduction in replication (P < .05). Incubation of MDCK cells in preservative solution at 4.degree. C under hypoxic conditions resulted in a time-dependent reduction in synthetic and replicative capacity that plateaued at 24 hr (P < .01). The next step was to simulate the clinical situation by combining treatments. MDCK cells were incubated for 24 hr in preservative solution under hypoxic conditions at 4.degree. C, and then CsA was added at defined intervals. The addition of CsA before 24 hr resulted in a significant decrease in cell replication (P < .05) compared with CsA addition after 48 hr. Simialr results were obtained with cells incubated for 48 hr in preservative solution with hypoxia. These data suggest that renal injury from ischemia and cold storage requires a period of cellular repair and replication. Administration of CsA before this period results in further renal injury. Our analysis offers an explanation of CsA nephrotoxicity seen in the human situation and, therefore, may provide a model for studying human nephrotoxicity.