Uptake of l‐Glutamate and Taurine in Neuroblastoma Cells with Altered Fatty Acid Composition of Membrane Phospholipids

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Abstract
Effects of altered composition of membrane lipids on high‐affinity uptake of l‐glutamate and taurine were studied in an established neuroblastoma cell line M1. Increase in participation of certain fatty acids (20: 5ω3 and 22: 5ω3) as constituents of membrane lipids resulted in a fourfold increase in the maximum initial rate of l‐glutamate uptake (Vmax) while increase in Vmax of taurine uptake was much smaller. Neither structural requirements of l‐glutamate uptake nor passive permeability of the membrane to l‐glutamate or taurine seemed to be influenced by the alterations in the lipid composition. Since increased proportions of 20: 5ω3 and 22: 5ω3 in the membrane phosphatides caused no dramatic changes in kinetic parameters of taurine uptake and incorporation of either linoleic or linolenic acid alone into the phosphatides had only a relatively small effect on some of the measured parameters, the possibility of a specific relationship between 22: 5ω3 and/or 20: 5ω3 and l‐glutamate uptake is discussed. Unlike l‐glutamate uptake systems in other preparations, the high‐affinity uptake system of l‐glutamate in neuroblastoma cells did not readily accept l‐aspartate as a substrate.