Modulation of Ca2+ and Na+ transport by taurine in heart and vascular smooth muscle.
Using the whole-cell voltage clamp technique, taurine was found to affect different types of various ionic currents including T and L-type Ca2+ currents, slow Na+ and fast Na+ currents as well as the delayed outward K+ current. Also, in normal situations, taurine had no effect on the Na(+)-Ca2+ exchange current. The effect of taurine on the different types of ionic currents appears to depend on [Ca2+]o and [Ca2+]i and may also vary according to the tissue or cell type studied. Using standard Ca2+ imaging techniques, short-term exposure (10 to 20 min) of single heart cells and aortic vascular smooth muscle cells was found to increase total intracellular free Ca2+ in a dose-dependent manner. However, using 3-dimensional Ca2+ and Na+ imaging techniques, long-term exposure of heart and vascular smooth muscle cells to taurine was found to decrease both nuclear and cytosolic Ca2+ without significantly changing either nuclear or cytosolic Na+ levels. Long-term exposure to taurine was found to prevent cytosolic and nuclear increases of Ca2+ induced by permanent depolarization of heart cells with high [K+]o. This preventive effect of taurine on nuclear Ca2+ overload was associated with an increase of both cytosolic and nuclear free Na+. Thus, the effect of long-term exposure to taurine on intranuclear Ca2+ overload in heart cells seems to be mediated via stimulation of sarcolemma and nuclear Ca2+ outflow through the Na(+)-Ca2+ exchanger.
Bkaily
G
G
Department of Physiology and Biophysics, Faculty of Medicine, Université de Sherbrooke, Quebec, Canada.
Haddad
G
G
Jaalouk
D
D
Gros-Louis
N
N
Benchekroun
M T
MT
Naik
R
R
Pothier
P
P
D'Orléans-Juste
P
P
Bui
M
M
Wang
S
S
Sperelakis
N
N
D000818:Animals; D000831:Animals, Newborn; D001013:Aorta, Thoracic / Q000187:drug effects / Q000502:physiology*; D001692:Biological Transport / Q000187:drug effects; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000187:drug effects / Q000502:physiology; D002642:Chick Embryo; D004730:Endothelium, Vascular / Q000502:physiology; D005260:Female; D006321:Heart / Q000187:drug effects / Q000502:physiology*; D006325:Heart Atria; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology*; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology; D011817:Rabbits; D012964:Sodium / Q000378:metabolism*; D015222:Sodium Channels / Q000187:drug effects / Q000502:physiology; D013654:Taurine / Q000494:pharmacology*
D015220:Calcium Channels; D015221:Potassium Channels; D015222:Sodium Channels; D013654:Taurine; D012964:Sodium; D002118:Calcium