Permeability of human erythrocytes to ammonia and weak acids.

KLOCKE, ROBERT A., KAJSA K. ANDERRSON.HAROLD H. ROT. MAN, AND ROBERT E. FORSTER. Permeability of human ery throcy tes to ammonia and weak acids. Am. J. Physiol. 222(3): 1004-1013. 1972.We have developed a continuous-flow rapid-reaction apparatus, using a glass pH electrode, capable of measuring changes in pH of ho.01 unit as early as 0.01 set after mixing. With this apparatus we have measured the change of extracellular pH with time following mixture of a suspension of about 2570 fresh human red cells in saline with solutions of NH3 or of one of seven weak acids in saline. From these data we calculated the permeability of the red cell membrane for the unionized NH3 or acid. The average permeability of the human red cell at 37 C in centimeters per second for NH3 , was 1.08 X 10S2; for acetic acid, 1.44 X 1w3; for barbituric acid, 8.75 X 1 Oe4; for butyric acid, 1.10 X 10e2; for formic acid, 1.52 X 10V3; for lactic acid, 1.13 X le3; for propionic acid, 4.93 X 10B3; and for valeric acid, 2.70 X 10m2. The rate of NH3 and formic acid movement into the red cells was not altered by the simultaneous flux of water into or out of the cell produced by osmotic gradients as great as -88 and + 1,100 mOsm/liter, respectively. We present theoretical arguments that any effect of experimentally achievable fluid fluxes through the red cell membrane upon simultaneous solute flux (“solvent drag”) would be so small as to be difficult to detect.