title: Thiol group control of sodium-lithium countertransport kinetics in uraemia: evidence of a membrane abnormality affected by haemodialysis.
abstract: Uraemia affects erythrocyte metabolism and membrane function but no consistent effect on Na/Li countertransport (CT) has been reported. We report only small differences in Na/Li CT at 150 mmol/l Na over haemodialysis, but major differences in other properties of Na/Li CT. The Km for external sodium and Vmax both increased during haemodialysis but the Vmax/Km ratio, which was greater than normal, was not affected. The thiol reagent, N-ethylmaleimide (NEM), which causes a decrease in Km and Vmax in normal subjects, had no effect on Km in the predialysis erythrocytes. After haemodialysis, the sensitivity of Na/Li CT to NEM was improved. The changes in Na/Li CT kinetics were not related to changes in membrane lipid fluidity or plasma lipids. These observations suggest that uraemia affects a thiol group that controls Na/Li CT kinetics and that haemodialysis temporarily improves this aspect of membrane function.
authors.affiliation: Department of Medicine (Nephrology), Freeman Hospital, Newcastle-upon-Tyne, UK.
authors.forename: P A
authors.initials: PA
authors.lastname: Rutherford
authors.forename: T H
authors.initials: TH
authors.lastname: Thomas
authors.forename: J
authors.initials: J
authors.lastname: O'Kelly
authors.forename: I C
authors.initials: IC
authors.lastname: West
authors.forename: R
authors.initials: R
authors.lastname: Wilkinson
mesh_terms: D000368:Aged; D017920:Antiporters / Q000187:drug effects / Q000378:metabolism*; D004910:Erythrocyte Membrane / Q000187:drug effects / Q000378:metabolism; D004912:Erythrocytes / Q000187:drug effects / Q000378:metabolism*; D005033:Ethylmaleimide / Q000494:pharmacology*; D005260:Female; D006801:Humans; D017136:Ion Transport / Q000187:drug effects; D007700:Kinetics; D008094:Lithium / Q000378:metabolism; D008297:Male; D008560:Membrane Fluidity / Q000187:drug effects; D008875:Middle Aged; D006435:Renal Dialysis; D012964:Sodium / Q000378:metabolism; D013439:Sulfhydryl Reagents / Q000494:pharmacology*; D014511:Uremia / Q000097:blood* / Q000628:therapy
chemical_list: D017920:Antiporters; D013439:Sulfhydryl Reagents; C045885:sodium-lithium countertransporter; D008094:Lithium; D012964:Sodium; D005033:Ethylmaleimide