A KINETIC ANALYSIS OF SODIUM DEPENDENT GLUTAMIC ACID TRANSPORT IN PERIPHERAL NERVE

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Abstract
—The kinetics of sodium dependent glutamic acid transport have been studied in desheathed frog sciatic nerve. Initial velocities have been measured as a function of both glulamic acid and sodium concentration. Lineweaver–Burk plots are constructed from these data, and the kinetic constants describing uptake are estimated. Vmax is unaffected by sodium concentration, which implies that translocation is not directly affected by sodium. K1 is sodium dependent, which implies that sodium affects the affinity of the carrier for glutamic acid. Reciprocal plots of velocity vs [Na] or K1 vs 1/[Na] are linear, suggesting that glutamic acid and sodium are co‐transported on a one‐to‐one basis. t, the sodium concentration giving half maximal velocity of uptake, was found to vary from about 57 mm to 48 mm at glutamic acid concentrations of 1.0–10.0 ± 10−6m. A model of a mechanism by which sodium and glutamate could be co‐transported is presented; the model is in very good agreement with the experimental data.