Acid-base effects of altering plasma protein concentration in human blood in vitro.
We altered the concentration of plasma proteins in human blood in vitro by adding solutions with [Na+], [K+], and [Cl-] resembling those in normal blood plasma, either protein-free or with a high concentration of human albumin. After equilibrating the samples with a gas containing 5% CO2-12% O2-83% N2 at 37 degrees C, we measured pH, PCO2, and PO2; in separated plasma, we determined the concentrations of total plasma proteins and albumin and of the completely dissociated electrolytes (strong cations Na+, K+, Mg2+ and anions Cl-, citrate3-). With PCO2 nearly constant (mean = 35.5 Torr; coefficient of variation = 0.02), lowering plasma protein concentration produced a metabolic alkalosis, whereas increasing plasma albumin concentration gave rise to a metabolic acidosis. These acid-base disturbances occurred independently of a minor variation in the balance between the sums of strong cations and anions. We quantified the dependence of several acid-base variables in plasma on albumin (or total protein) concentration. Normal plasma proteins are weak nonvolatile acids. Although their concentration is not regulated as part of acid-base homeostasis, hypoproteinemia and hyperalbuminemia per se produce alkalosis and acidosis, respectively.
D000136:Acid-Base Equilibrium; D001798:Blood Proteins / Q000502:physiology*; D002245:Carbon Dioxide / Q000097:blood; D004573:Electrolytes / Q000097:blood; D006801:Humans; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D010100:Oxygen / Q000097:blood; D010313:Partial Pressure; D012709:Serum Albumin / Q000502:physiology
D001798:Blood Proteins; D004573:Electrolytes; D012709:Serum Albumin; D002245:Carbon Dioxide; D010100:Oxygen