Acid-base effects of altering plasma protein concentration in human blood in vitro

J Appl Physiol (1985). 1986 Dec;61(6):2260-5. doi: 10.1152/jappl.1986.61.6.2260.


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.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Acid-Base Equilibrium*
  • Blood Proteins / physiology*
  • Carbon Dioxide / blood
  • Electrolytes / blood
  • Humans
  • Hydrogen-Ion Concentration
  • In Vitro Techniques
  • Oxygen / blood
  • Partial Pressure
  • Serum Albumin / physiology


  • Blood Proteins
  • Electrolytes
  • Serum Albumin
  • Carbon Dioxide
  • Oxygen