Activity measurements of calcium, sodium, potassium, and chloride after equilibrium dialysis used to show lack of evidence for protein interference with calcium electrodes.

We measured the activity of Ca2+, Na+, K+, and Cl- with ion-selective electrodes after equilibrium dialysis of solutions with different albumin concentrations. The calculated Donnan ratio was the same for all ions in the same solution and increased with the albumin concentration, as predicted by the Donnan theory. The Donnan distribution ratio for Ca2+ was similar, as determined with instruments from three different manufacturers. For healthy subjects and patients with renal stone disease, we did not find any correlation between serum concentrations of ionized calcium and albumin. The discordance between measured ionized calcium and albumin-corrected total calcium depended on the correction algorithm we utilized. The difficulties of absolutely proving or disproving a protein error in these measurements are discussed, but our data are not consistent with protein being a source of error in measurements of ionized calcium.

The Influence of Experimental Anaemia on Blood Acid-Base Regulation In Vivo and In Vitro in the Starry Flounder (Platichthys Stellatus) and the Rainbow Trout (Salmo Gairdneri)

Severe experimental anaemia caused a rise in Pcoco2 and an associated fall in pH (respiratory acidosis) in arterial and venous blood of both flounder and trout in vivo. In some trout, but not in flounder, there was also a rise in blood lactate, indicating metabolic acidosis. In vitro, blood buffer capacities declined with haematocrit, a factor which contributed to the extent of the acidoses in vivo. However, haematocrit did not influence the pK1 of the plasma HCO3−/H2CO3 system or the actual measurement of blood pH. The Donnan ratio for HCO3− varied linearly with pH over the range 7.0–7.6, indicating a passive distribution of HCO3− across the trout erythrocyte. The present data, together with other recent results, indicate that the teleost red blood cell does play a role in plasma HCO3− dehydration and CO2 excretion, and therefore opposes the theory of Haswell & Randall (1978) that the erythrocyte is functionally impermeable to HCO3−.

Temperature-induced changes in blood acid-base status: Donnan rCl and red cell volume

The Donnan ratio for chloride ion (rCl) was determined for human red cells in plasma utilizing 36Cl. The effect of altered PCO2 and pH on rCl was followed in two ways. CO2 partial pressure was varied (1–1.5% CO2 in O2; pH range 7.1–7.9) at 37.5 degrees C (isothermal); PCO2 and pH were also changed by altering temperature (range 5–45 degrees C) at constant CO2 content (temperature induced). At pH 7.4 and 37.5 degrees C, rCl was 0.631 +/- 0.0269 (SE, N = 5); isothermal drcl/dpH = -0.306 +/- 0.0234. When measured under conditions of variable temperature at constant CO2 content (pH range 7.3–7.9), drcl/dpH = .018 +/- 0.0232, significantly different from isothermal response (P less than 0.001). Hematocrit (H) changes with pH for conditions of initial H(7.4) of 0.45, under these conditions were also determined: isothermal dH/dpH = -0.031 +/- 0.0019; temperature induced, -0.004 +/- 0.0009. Temperature change alone at constant carbon dioxide content produces no significant change in distribution of chloride ions or water between erythrocyte and plasma compartments.