Vol. 284, Issue 1, 142-150, 1998

Role of Protein Thiols in Inhibition of Sodium-Coupled Glucose Uptake by Cisplatin in Renal Brush-Border Membrane Vesicles

Sophie Potdevin , Françoise Courjault-Gautier, Bertrand Monegier Du Sorbier, Pierre Ripoche and Hervé J. Toutain

Service de Biologie Cellulaire (S.P., P.R.), Centre d'Etudes Nucléaires de Saclay, CEA, Gif-sur-Yvette, France; Laboratoire de Spectromètrie de Masse, Département d'Analyse Chimique (B.M.S.) and Laboratoire de Toxicologie Expérimentale, Département Sécurité du Médicament (S.P., F.C.-G., H.J.T.), CRVA, Rhône-Poulenc Rorer S.A., Vitry sur Seine, France

The potent anticancer drug cis-diamminedichloroplatinum (II) (cDDP) impairs glucose reabsorption by renal proximal tubular cells, which leads to glucosuria. We investigated the direct effect of cDDP (0.04-2 mM) on the Na⁺/glucose cotransport system in brush-border membrane (BBM) vesicles from the rabbit renal cortex. cDDP induced 1) concentration-dependent inhibition of the Na⁺/glucose cotransport system, by decreasing its V_max value and, to a lesser extent, its affinity, and 2) platinum binding to BBM vesicles, associated with decreases in protein-bound thiols. cDDP produced weaker inhibition of the Na⁺/glucose cotransport system and platinum binding to BBM vesicles than did highly reactive cDDP hydrated derivatives, with similar decreases in protein-bound thiols. Treatment with diethyldithiocarbamic acid (a drug protecting against cDDP nephrotoxicity), immediately after cDDP exposure, 1) partially lifted the cDDP-induced inhibition of the Na⁺/glucose cotransporter, 2) reduced platinum binding to BBM vesicles, but 3) did not modify the cDDP-induced decrease in protein-bound thiols. Our findings strongly suggest that cDDP-induced inhibition of the Na⁺/glucose cotransport system is mainly mediated by direct chemical binding of cDDP and/or its hydrated derivatives to essential sulfhydryl groups of the transport protein and may also involve other nucleophilic groups (e.g., the -SCH₃ group of methionines).