Amino acid uptake systems in lizard and chick brain cells.

The uptake of seven amino acids, alpha-aminoisobutyric acid (AIB), cyclo-leucine (cyclo-Leu), gamma-aminobutyric acid (GABA), glycine (Gly), glutamic acid (Glu), lysine (Lys), and taurine (Tau), representatives of different amino acid transport systems, was studied in slices of brain from Tokay lizards and White Leghorn chicks. In descending order, the rate of the initial uptake of the amino acids in both species was Glu greater than Gly greater than GABA greater than Cyclo-Leu greater than AIB greater than Lys greater than Tau. The substrate specificities and the differences in sodium and temperature dependence of the uptake of the amino acids indicate the presence of several distinct amino acid transport systems, some sodium-dependent and some sodium-independent. The structural specificity of amino acid transport classes in the brain of these species is similar to that in other vertebrate brain preparations.