Active transport of taurine in rabbit jejunal brush-border membrane vesicles.
The characteristics of taurine uptake in rabbit jejunal brush-border membrane vesicles were investigated. Taurine was transiently accumulated inside the vesicles against a concentration gradient when an inwardly directed NaCl gradient was imposed across the membrane. Uptake of taurine showed an absolute requirement for both Na+ and Cl-. The NaCl gradient-dependent taurine uptake was stimulated by a valinomycin-induced, inside-negative, K+-diffusion potential, suggesting that the uptake process was electrogenic. The uptake system exclusively interacted with beta-amino acids of small size, but had no affinity for alpha-amino acids. Kinetic analysis revealed that the system exhibited high affinity for taurine (Kt = 14.4 +/- 0.5 microM). Taurine uptake was greatly influenced by extravesicular concentrations of Na+ and Cl-. The Cl- stoichiometry was found to be one. In the presence of Cl-, taurine uptake was sigmoidally related to Na+ concentration, and the Na+ stoichiometry was calculated to be three. Thus three Na+ and one Cl- were involved per transport of one taurine molecule. The uptake process was not affected by other transport inhibitors such as amiloride, harmaline, furosemide, and 4,4'-diisothiocyanostilbene-2,2'-disulfonate.
Miyamoto
Y
Y
Department of Cell and Molecular Biology, Medical College of Georgia, Augusta 30912-2100.
Tiruppathi
C
C
Ganapathy
V
V
Leibach
F H
FH
D000818:Animals; D000838:Anions; D001693:Biological Transport, Active / Q000187:drug effects; D002712:Chlorides / Q000494:pharmacology; D007583:Jejunum / Q000378:metabolism* / Q000648:ultrastructure; D007700:Kinetics; D008564:Membrane Potentials; D008871:Microvilli / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism; D011189:Potassium Chloride / Q000494:pharmacology; D011817:Rabbits; D012964:Sodium / Q000494:pharmacology; D012965:Sodium Chloride / Q000494:pharmacology; D013654:Taurine / Q000378:metabolism*; D014634:Valinomycin / Q000494:pharmacology
D000838:Anions; D002712:Chlorides; D013654:Taurine; D014634:Valinomycin; D012965:Sodium Chloride; D011189:Potassium Chloride; D012964:Sodium; D011188:Potassium