Effect Of Ethanol On L-type Calcium Channel Current And Voltage-dependent Sodium Channel Current In Guinea Pig Ventricular Myocytes

Objective: Establishing the whole-cell patch-clamp technique to observe the effect of ethanol with different concentration on L-type calcium channel (Ica,L)current and voltage-dependent sodium channel(INa) current in guinea pig ventricular myocytes, and to explore its significance in ethanol-induced cardiomyocyte injury.Methods: Single ventricular myocytes were isolated enzymatically from the ventricles of guinea pig. Ethanol experimental models of ventricular myocytes were established by superfusion with ethanol for 5 minutes at a speed of 2ml/min. L-type calcium channel current and voltage-dependent sodium channel current were recorded using whole-cell patch-clamp technique. Peak current and current-voltage relationship(I-V) were obtained when superfusion with normal external solution, different concentration of ethanol respectively. Results: (1) Whole-cell patch-clamp recording technique was established, and highly stable whole cell ion channels' current curves of normal ventricular myocytes were ploted. (2) Ethanol, 24mM reduced the peak current of Ica,L from (11.04+0.95)pA/pF to (9.58+0.89)pA/pF (p<0.05,n = 5). Ethanol, 80mM reduced the peak current of ICa,L from (10.90+1.14)pA/pF to (8.91+0.81)pA/pF (p<0.05,n = 5). Ethanol, 240mM reduced the peak current of ICa,L from (10.82+0.86)pA/pF to (7.81+0.85)pA/pF (p<0.05,n=5). Ethanol inhibited the peak current of ICa,L concentration-dependently. The percentage of inhibition were (13.09+6.46)%,(17.92+7.91)% and (27.48+9.35)% respectively. Ethanol, 240mM vs 24mM p<0.05. (3) Ethanol, 24,80,240mM shifted the I-V of ICa,L upwardly. The contour of I-V keeped unchanged, and the peak current stimulating voltage remained 0mV .(4) Ethanol, 24mM reduced the peak current of INa from (149.20+7.89)pA/pF to (146.08+8.33)pA/pF (p>0.05,n = 5). Ethanol, 80mM reduced the peak current of INa from (148.43+9.04)pA/pF to (129.01+8.98)pA/pF (p<0.05,n = 5). Ethanol, 240mM reduced the peak current of Ina from (150.03+8.08)pA/pF to (117.44+15.15)pA/pF (p<0.05,n=5). Ethanol, 24mM did not affect the peak current of INa Ethanol, 80,240mM inhibited the peak current of Ina concentration-dependently. The percentage of inhibition were (13.08+3.1)% and (21.94+6.5)%, respectively. Ethanol, 240mM, 80mM vs 24mM p<0.05. (5) Ethanol, 24mM did not affect the I-V of INa- 80,240mM shifted the I-V of INa upwardly. The contour of I-V keeped unchanged, and the peak current stimulating voltage remained -3OmV .Conclusions: The Ica,L current inhibition by ethanol at clinically relevant concentration (24mM) contribute to a negative inotropic effect, action potential shortening and development of arrhythmias. Ethanol, 24mM did not affect Ina current, but a lethal concentration of ethanol(80mM) significantly inhibited. Therefore, an involvement of Iwa current suppression in the negative inotropic effects of ethanol or development of arrhythmias seems quite unlikely except in nearly lethal intoxication.