Cyclosporin-mediated increase in kidney glutathione and effects on gamma-glutamyl-cycle enzymes.

The unprecedented ability of cyclosporin A, when given for six days at a dose of 25 mg/kg/d or 50 mg/kg/d, to cause a marked and sustained increase in renal glutathione (GSH) concentration in rat kidney is described. This response was particular to the kidney insofar as the GSH concentration in the liver was not increased in response to a lower dose of cyclosporin and was decreased in the liver of animals treated with the higher dose of the drug. The increase in kidney GSH concentration did not appear to be due to an increased rate of production or to an inhibition of the degradation of the tripeptide. This suggestion is based on the finding that the activities of the GSH synthesis pathways, GSSG-reductase and gamma-glutamylcysteine synthetase, were unchanged or decreased, respectively, and those of the catabolic enzymes, GSH-peroxidase and gamma-glutamyltranspeptidase, were unchanged or increased, respectively. It is suggested that the elevation of renal GSH content in the face of diminished synthetic capacity and an apparent increased utilization may result from an enhanced uptake of GSH as the result of alterations caused by cyclosporin in the renal transport system.