Tryptophan transport into plasma membrane vesicles derived from rat brain synaptosomes.
Tryptophan uptake by membrane vesicles derived from rat brain was investigated. The uptake is dependent on the Na+ gradient [Na+] outside greater than [Na+] inside, and is maximal when both Na+ and Cl- are present. The uptake represents transport into an osmotically active space and not a binding artifact, as indicated by the effect of increasing the medium osmolarity. The uptake of tryptophan is stimulated by a membrane potential (interior negative) as demonstrated by the effects of the ionophores valinomycin and carbonyl cyanide m-chlorophenylhydrazone and anions with different permeabilities. Kinetic data show that tryptophan is accumulated by two systems with different affinities. Ouabain, an inhibitor of Na+,K+-activated ATPase, does not affect tryptophan transport. The uptake of tryptophan is inhibited by high concentrations of phenylalanine, tyrosine, leucine, and 3,4-dihydroxyphenylalanine.
D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D001921:Brain / Q000378:metabolism*; D007476:Ionophores / Q000494:pharmacology; D007700:Kinetics; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D013570:Synaptic Membranes / Q000378:metabolism*; D013574:Synaptosomes / Q000187:drug effects / Q000378:metabolism*; D014364:Tryptophan / Q000378:metabolism*
D007476:Ionophores; D008565:Membrane Proteins; D014364:Tryptophan