Distinction between chloride-dependent transport systems for taurine and beta-alanine in rabbit ileum.
This study describes the influx of taurine and beta-alanine across the brush-border membrane of rabbit distal ileum. The kinetics of JmcTau [concentration at which half-maximal activation occurs (K1/2) = 41 microM and Jmax = 24 nmol.cm-2.h-1] are consistent with the kinetics of taurine uptake by jejunal brush-border vesicles. The taurine carrier differs from the beta-alanine carrier by being insensitive to leucine inhibition and by the jejunoileal variation of influx along the small intestine. The K1/2 for sodium and chloride activation of the beta-alanine carrier (48 and 8 mM, respectively) differ markedly from the values reported for the taurine carrier. In addition, taurine is not transported by the beta-alanine carrier. Thus the study demonstrates that the taurine and beta-alanine carriers are separate entities, and it adds to the imino and the taurine carriers the beta-alanine carrier as a third chloride-dependent intestinal transporter of amino acids.
Munck
L K
LK
Department of Medicine F, Gentofte Hospital, Copenhagen, Denmark.
Munck
B G
BG
D026905:Amino Acid Transport Systems; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002352:Carrier Proteins / Q000378:metabolism; D002712:Chlorides / Q000494:pharmacology*; D007082:Ileum / Q000378:metabolism*; D007098:Imino Acids / Q000378:metabolism; D008871:Microvilli / Q000378:metabolism; D011817:Rabbits; D012964:Sodium / Q000494:pharmacology; D013654:Taurine / Q000493:pharmacokinetics*; D015091:beta-Alanine / Q000493:pharmacokinetics*
D026905:Amino Acid Transport Systems; D002352:Carrier Proteins; D002712:Chlorides; D007098:Imino Acids; D015091:beta-Alanine; D013654:Taurine; D012964:Sodium