Kinetics of Chloride-Bicarbonate Exchange Across the Human Red Blood Cell Membrane

Kinetics of Chloride-Bicarbonate Exchange Across the Human Red Blood Cell Membrane We use a fluorescent probe of [Cl−], 6-methoxy-N-(3-sulfopropyl)quinolinium (SPQ), to study Cl−/HCO− 3 exchange in human erythrocyte ghosts in a stopped-flow apparatus at 4°C. The quench constant of SPQ in our Cl−/HCO− 3/HPO= 4 system at pH 7.4 is 0.065 ± 0.005 mm −1. The time course of Cl−/HCO− 3 exchange does not follow a single exponential function at 4°C and we propose an extended ping-pong model in which slippage is explicitly considered in order to account for this phenomenon. The solution of the system of equations generated by our model is a double exponential function which fits the time course of Cl−/HCO− 3 exchange. Our results confirm the predictions of the model concerning the functional dependence of the two rate constants. One rate constant (k 1) is independent of medium composition; it is determined by the sum of the two slippage rate constants and its value is 1.04 ± 0.14 sec−1. The other rate constant (k 2) varies inversely with [Cl−]; the regression line is 1/k 2= 18.8 sec − 0.095 mm −1sec [Cl−]. The Journal of Membrane Biology Springer Journals

Kinetics of Chloride-Bicarbonate Exchange Across the Human Red Blood Cell Membrane

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Copyright © Inc. by 1997 Springer-Verlag New York
Life Sciences; Biochemistry, general; Human Physiology
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