INFLUX OF GLUTAMIC ACID IN PERIPHERAL NERVE-CHARACTERISTICS OF INFLUX

Abstract— —The influx of glutamic acid in frog sciatic nerve has been studied by monitoring the disappearance of 14C labelled compound from the bathing medium. After 5hr of incubation in 10 −6m non‐labelled l‐glutamic acid and 0·01, μc/ml labelled isotope, the intracellular concentration of labelled glutamic acid is about 15 times the concentration in the bathing medium; however, there appears to be a net loss of non‐labelled compound with incubation. Uptake of L,‐glutamic acid is accompanied by conversion of significant amounts of labelled E‐glutamic acid to carbon dioxide and glutamine; small amounts of γ‐aminobutyric acid and aspartic acid are also formed. The rate of disappearance of labelled l‐glutamic acid decreases with increasing concentration of non‐labelled isotope in the bathing medium. Construction of a Lineweaver‐Burk plot from initial velocities of influx yields an average Vm of 4·02 × 10−9 moles/g/min and an average Km. of 3·23 × 10 −5 moles/l. The influx of glutamic acid is highly specific with regard to molecular structure; of the compounds tested, only l‐glutamine, l‐glutamic acid, GABA, l‐lysine, and l‐aspartic acid are taken up, and only l‐aspartic acid will compete with l‐glutamic acid for uptake. Copyright © 1968, Wiley Blackwell. All rights reserved