title: Kinetics of bicarbonate-chloride exchange across the human red blood cell membrane.
abstract: The kinetics of bicarbonate-chloride exchange across the human red cell membrane was studied by following the time course of extracellular pH in a stopped-flow rapid-reaction apparatus during transfer of H+ into the cell by the CO2 hydration-dehydration cycle, under conditions where the rate of the process was determined by HCO3--Cl- exchange flux across the membrane. The flux of bicarbonate increased linearly with [HCO3-] gradient from 0.6 to 20 mM across the red cell membrane at both 37 degrees C and 2 degrees C, and decreased as transmembrane potential was increased by decreasing extracellular [Cl-]. An Arrhenius plot of the rate constants for the exchange indicates that the Q10 is strongly dependent on temperature, being about 1.7 between 24 degrees C and 42 degrees C and about 7 between 2 degrees C and 12 degrees C. These data agree well with the published values for Q10 of 1.2 between 24 degrees C and 40 degrees C and of 8 between 0 degrees C and 10 degrees C. The results suggest that different processes may determine the rate of HCO3--Cl- exchange at low vs. physiological temperatures, and that the functional (and/or structural) properties of the red cell membrane vary markedly with temperature.
mesh_terms: D001639:Bicarbonates / Q000378:metabolism*; D001692:Biological Transport; D002463:Cell Membrane Permeability; D002712:Chlorides / Q000378:metabolism*; D004910:Erythrocyte Membrane / Q000378:metabolism*; D004912:Erythrocytes / Q000378:metabolism*; D005110:Extracellular Space / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D007424:Intracellular Fluid / Q000378:metabolism; D007700:Kinetics; D013696:Temperature
chemical_list: D001639:Bicarbonates; D002712:Chlorides