EVIDENCE FOR SEPARATE SYSTEMS FOR THE TRANSPORT OF NEUTRAL AND BASIC AMINO ACIDS ACROSS THE BLOOD‐BRAIN BARRIER

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Abstract
Abstract— The effects of high circulating concentrations of several amino acids on the free amino acids of rat brain were measured, to see whether or not the results followed any consistent pattern. High circulating concentrations of large, neutral amino acids (phenylalanine, valine or isoleucine) caused significantly decreased values only of other large, neutral amino acids in the brains. High circulating concentrations of the basic amino acids lysine or arginine caused significantly decreased values only of each other. The data suggest that there are separate systems for the transport of neutral and basic amino acids across the blood‐brain barrier. The effects of valine and lysine on the uptake by brain and the con‐vulsant action of allylglycine (a neutral amino acid) were consistent with the concept of separate systems for the transport of amino acids across the blood‐brain barrier. Valine inhibited the uptake by brain and the convulsant action of allylglycine in mice, but lysine did not. The data suggest that allylglycine and valine are transported into the brain by a common mechanism that does not transport lysine.