Sodium ion binding in human serum.
The amount of sodium ion binding in human sera and in dialyzed human sera was estimated from standard-addition titrations with an ion-selective electrode and from measurements of 23Na nuclear magnetic resonance (NMR) linewidth. For the untreated sera, maximum binding was 1% (1.4 mmol/L) as indicated by NMR; virtually no binding was found via the titration method. For dialyzed sera with low-sodium, normal-protein content, NMR indicated that sodium binding was less than 1.3% (0.14 mmol/L). The same dialyzed fluid analyzed with ion-selective electrodes shows no sodium binding, within the limits of experimental error (+/- 4%). Sodium ion binding to serum protein thus contributes only minimally to differences in sodium measurements observed between the direct (undiluted) ion-selective electrode and flame-photometric methods.
D001798:Blood Proteins / Q000378:metabolism*; D002624:Chemistry, Clinical / Q000379:methods; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D011485:Protein Binding; D012964:Sodium / Q000097:blood*
D001798:Blood Proteins; D012964:Sodium