Taurine indirectly increases [Ca]i by inducing Ca2+ influx through the Na(+)-Ca2+ exchanger.
Recent studies in heart cells have shown taurine to induce a sustained increase of both intracellular Ca2+ and Na+. These results led us to believe that the increase in Na+ by taurine could be due to Na+ entry through the taurine-Na+ cotransporter which in turn favours transarcolemmal Ca2+ influx through Na(+)-Ca2+ exchange. Therefore, we investigated the effect of beta-alanine, a blocker of the taurine-Na+ cotransporter and low concentrations of CBDMB (a pyrazine derivative, 5-(N-4chlorobenzyl)-2',4'-dimethylbenzamil), a Na(+)-Ca2+ exchanger blocker on taurine-induced [Ca]i increase in embryonic chick heart cells. Using Fura-2 Ca2+ imaging and Fluo-3Ca2+ confocal microscopy techniques, taurine (20 mM) as expected, induced a sustained increase in [Ca]i at both the cytosolic and the nuclear levels. Preexposure to 500 microM of the blocker of the taurine-Na+ cotransporter, beta-alanine, prevented the amino acid-induced increase of total [Ca]i. On the other hand, application of beta-alanine did not reverse the action of taurine on total [Ca]i. However, low concentrations of the Na(+)-Ca2+ exchanger blocker, CBDMB, reversed the taurine-induced sustained increase of cytosolic and nuclear free calcium (in presence or absence of beta-alanine). Thus, the effect of taurine on [Ca]i in heart cells appears to be due to Na+ entry through the taurine-Na+ cotransporter which in turn favours transarcolemmal Ca2+ influx through the Na(+)-Ca2+ exchanger.
Bkaily
G
G
MRCC Group on Immuno-cardiovascular Interaction, Department of Anatomy and Cell Biology, Faculty of Medicine, University of Sherbrooke, Québec, Canada.
Jaalouk
D
D
Sader
S
S
Shbaklo
H
H
Pothier
P
P
Jacques
D
D
D'Orléans-Juste
P
P
Cragoe
E J
EJ
Bose
R
R
D000584:Amiloride / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002469:Cell Separation; D002478:Cells, Cultured; D002642:Chick Embryo; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism; D016257:Fura-2 / Q000378:metabolism; D006352:Heart Ventricles / Q000166:cytology / Q000378:metabolism; D007424:Intracellular Fluid / Q000187:drug effects / Q000378:metabolism; D017136:Ion Transport / Q000187:drug effects*; D009206:Myocardium / Q000201:enzymology / Q000378:metabolism; D019831:Sodium-Calcium Exchanger / Q000378:metabolism*; D013654:Taurine / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D013997:Time Factors; D015091:beta-Alanine / Q000494:pharmacology
D019831:Sodium-Calcium Exchanger; C054391:5-(N-4-chlorobenzyl)-N-(2',4'-dimethyl)benzamil; D015091:beta-Alanine; D013654:Taurine; D000584:Amiloride; D002118:Calcium; D016257:Fura-2