Influence of protein content upon the electrolyte composition of lymph and plasma

The concentration of Na+ and Cl' is higher in renal hilar lymph (HL) than in arterial (P) or renal venous plasma or thoracic duct lymph (TDL). The purpose of the present study was to test the theory that this is the consequence of differences in protein content of lymph and plasma rather than a reflection of renal function. Samples of P, HL and TDL were obtained from dogs and analysed for Na+, Cl', K+ and Ca++. The samples were then centrifuged through an ultrafiltration membrane to remove the protein and reanalysed for electrolyte content. Ca++ concentrations were reduced by 30-40% in the (protein-free) filtrate. This was attributed to protein binding. Na+ and Cl' concentrations were raised minimally (2.0 mEq/L and 5.0 mEq/L respectively) in protein-free filtrate of plasma, but not in protein-free filtrate of lymph. It was concluded that the relative protein concentration in lymph and plasma are not an important influence on Na+ and Cl' concentrations.