title: Interaction of taurine with the fast Na-current in isolated rabbit myocytes.
abstract: We studied in whole cell configuration with the patch clamp method the effect of taurine on the macroscopic Na current in adult ventricular rabbit myocytes. Because these cells have a large surface [13,750 +/- 704 microns2 (19), mean +/- S.E.M. (n)], we reduced [Na]o to 45 mM and worked at room temperature to obtain acceptable voltage control. When the cells were held at -80 mV, taurine (20 mM) had the following effects: 1) The current voltage relationships crossed over so that taurine increased INa at potentials negative to -45 mV, and at more positive potentials it depressed the current; 2) taurine reduced the maximal Na conductance from 536.3 +/- 72.2 to 253.6 +/- 33.6 microS.cm-2; 3) the crossing over of the I/V curves was mainly caused by a hyperpolarizing shift of V1/2 of the steady-state activation by 6.3 mV; 4) the crossing over was independent of a -4.6 mV shift of V1/2 of the steady-state inactivation and 5) taurine increased significantly the time constant of reactivation between -90 and -70 mV, but we did not find evidence that taurine changed the time constant of inactivation between -40 and +20 mV. We conclude that positive to -45 mV taurine causes a block of INa channels that resembles that of local anesthetic antiarrhythmic drugs. Negative to -45 mV taurine counteracts the local anesthetic effect causing increased excitability and improved conduction in the range of the threshold potential and -45 mV.
authors.affiliation: Département de Physiologie et Biophysique, Faculté de Médecine, Université de Sherbrooke, Québec, Canada.
authors.forename: O F
authors.initials: OF
authors.lastname: Schanne
authors.forename: R
authors.initials: R
authors.lastname: Dumaine
mesh_terms: D000818:Animals; D006321:Heart / Q000187:drug effects* / Q000502:physiology; D066298:In Vitro Techniques; D011817:Rabbits; D015222:Sodium Channels / Q000187:drug effects*; D013045:Species Specificity; D013654:Taurine / Q000494:pharmacology*
chemical_list: D015222:Sodium Channels; D013654:Taurine