Taurine and beta-alanine transport in an established human kidney cell line derived from the proximal tubule.
The transport mechanisms of taurine and beta-alanine by an immortalized human embryonic kidney epithelial cell line (IHKE) were examined. The uptake of these beta-amino acids was characterized by two Na(+)-dependent transport components, whereas an inwardly directed H(+)-gradient only stimulated amino acid influx to a small extent and in the absence of sodium. Competition experiments revealed that taurine and beta-alanine drastically reduced the uptake of one another by the high-affinity Na(+)-dependent transport system. However, some alpha-amino acids could also compete with the beta-amino acids, but with a low affinity. Examinations of the effect of different anions on the Na(+)-dependent uptake of taurine at a low amino acid concentration (240 nM) revealed a specific requirement for Cl-, whereas Cl- had no measurable effect at a higher concentration (1.0 mM) of taurine. In addition, activation of taurine transport as a function of Na+ and Cl- concentration indicated a probable coupling ratio of 3 Na+/1 Cl-/1 taurine for the high-affinity carrier. Finally, cellular regulation of taurine transport was indicated by the finding that pretreatment with taurine containing media decreased the activity of the taurine transporter(s).
Jessen
H
H
Institute of Medical Biochemistry, University of Aarhus, Denmark.
D000838:Anions; D001693:Biological Transport, Active; D002352:Carrier Proteins / Q000378:metabolism; D002460:Cell Line; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007687:Kidney Tubules, Proximal / Q000378:metabolism*; D007700:Kinetics; D008562:Membrane Glycoproteins / Q000378:metabolism; D026901:Membrane Transport Proteins; D012965:Sodium Chloride; D013379:Substrate Specificity; D013654:Taurine / Q000378:metabolism*; D015091:beta-Alanine / Q000378:metabolism*; D000099247:Taurine Transporters
D000838:Anions; D002352:Carrier Proteins; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D012965:Sodium Chloride; D013654:Taurine; D015091:beta-Alanine; D000099247:Taurine Transporters