Effects of taurine on Ca2+ currents in young embryonic chick cardiomyocytes

The effects of taurine on L-type and T-type Ca2+ channels is isolated 3-day-old embryonic chick heart cells were examined at different intracellular Ca2+ concentrations ([Ca]i), using whole-cell voltage clamp techniques. Experiments were performed at room temperature (22 degrees C) and at a holding potential of -40 mV. When [Ca]i was pCa 7, addition of taurine to the bath solution reduced the L-type Ca2+ current (ICa(L)) at 0 mV by 56.3 +/- 2.8% (n = 5, P < 0.01) at 10 mM, and by 73.2 +/- 2.6% (n = 5, P < 0.001) at 20 mM. At pCa 10, ICa(L) was unaffected (7.2 +/- 3.1%, n = 5, P > 0.05) by 10 mM taurine and was enhanced by 47.3 +/- 2.4% (n = 5, P < 0.01) by 20 mM taurine. Control fast and slow time constants of inactivation at pCa 7 (at +10 mV) were 5.8 +/- 2.8 ms and 28.8 +/- 1.8 ms (n = 4), respectively; neither constant was modified by taurine. At pCa 10, the control fast and slow time constants were 15.8 +/- 1.0 and 67.7 +/- 3.8 ms (n = 4); the fast time constant was not affected by 10-20 mM taurine but the slow time constant was slowed by 14.5 +/- 2.9% (n = 4, P < 0.05) by 10 mM taurine and by 66.2 +/- 2.8% (n = 4, P < 0.001) by 20 mM taurine. The inactivation curve for ICa(L) was not modified by taurine.(ABSTRACT TRUNCATED AT 250 WORDS)