Characterization of a novel Na+-independent amino acid transporter in horse erythrocytes.
Horse erythrocytes are polymorphic with respect to L-alanine permeability. The present investigation compared the specificity, kinetics and cation-dependence of erythrocyte amino acid transport in two groups of thoroughbred horses, those with erythrocyte L-alanine permeabilities in the range 5-15 mumol/h per litre of cells (0.2 mM extracellular L-alanine, 37 degrees C) (transport-negative type) and those with L-alanine permeabilities in the range 450-700 mumol/h per litre of cells (transport-positive type). Transport-positive cells are shown to possess a novel high-affinity, stereospecific, Na+-independent transporter selective for neutral amino acids of intermediate size. This carrier system (provisional designation asc) operates preferentially in an exchange mode and is functionally absent from erythrocytes of transport-negative-type horses.
D000409:Alanine / Q000378:metabolism; D000596:Amino Acids / Q000097:blood*; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002414:Cations, Monovalent / Q000494:pharmacology; D003545:Cysteine / Q000494:pharmacology; D004912:Erythrocytes / Q000187:drug effects / Q000378:metabolism*; D006736:Horses; D012964:Sodium / Q000494:pharmacology; D013379:Substrate Specificity
D000596:Amino Acids; D002414:Cations, Monovalent; D012964:Sodium; D003545:Cysteine; D000409:Alanine