Cyclosporine A induced lipid peroxidation and influence on glucose-6-phosphatase in rat hepatic and renal microsomes.

The in vitro effect of cyclosporine A (CsA) on lipid peroxidation (LPO) in hepatic and renal microsomes (male Wistar rats) were investigated either with different CsA concentrations (0.3-1000 micrograms/ml), incubation time 3 h or for different periods of time (0.5-3.0 h) at a CsA concentration of 1000 micrograms/ml. LPO was monitored by measuring the formation of malondialdehyde (MDA) using the thiobarbituric acid assay. Furthermore the influence of CsA on the microsomal enzyme glucose-6-phosphatase was investigated. CsA caused a time- and concentration-dependent increase of LPO in hepatic and renal microsomes. The lowest CsA concentration which produced a significant increase in MDA production amounted to 1 microgram/ml for hepatic microsomes and 3 micrograms/ml for renal microsomes. Under identical experimental conditions, the MDA production by hepatic microsomes was 3 to 5 fold higher than by renal microsomes. Addition of the radical scavenger alpha-tocopherol (1 mM) to the incubation medium decreased the CsA-caused microsomal MDA production. Regarding the microsomal enzyme, CsA decreased the specific activity of glucose-6-phosphatase in a time- and concentration-dependent fashion. Compared to microsomal MDA production, higher CsA concentrations were necessary to effect on specific enzyme activity. The results suggest, that production of free radicals and subsequently lipid peroxidation could participate in cyclosporine A induced hepato- and nephrotoxicity.