The effect of levobunolol hydrochloride on the calcium and potassium channels in isolated ventricular myocytes of guinea pig

Abstract

The effects of levobunolol hydrochlorid (Bun) on the type L calcium channel currents (I_ca and delayed rectifier potassium channel currents (I_k) in isolated ventricular myocytes of guinea pig were studied by using patch clamp whole cell recording techniques. The results were showed that: 1) Bun caused a dosedependent decrease in I_ca and a dose-dependent increase in I_k of the ventricular myocytes. The threshold concentrations of Bun for I_ca and I_k were 10⁻⁸ mol/L and 10⁻⁷ mol/L respectively. The maximum effective concentration of Bun for both I_ca and I_k was 3 × 10⁻⁵ mol/L, and half-maximal concentration Was 3 × 10⁻⁶ mol/L; 2) I_k was blocked by 2 × 10⁻⁶mol/L tetraethylammonium (TEA). A concentration of 3 × 10⁻⁶ mol/L Bun showed a decreasing effect on the Ic as revealed by the current-voltage relationship curve, i.e., Bun caused an elevation of the curve; 3) When I_ca was blocked by 2X10⁻⁶ mol/L Isoptin (Verapamil), at a concentration of 3 × 10⁻⁶ mol/L Bun showed an increasing effect on Ik and the effect could be blocked by TEA- The above-mentioned results indicated that Bun had an inhibitory effect on I_ca and a fascilitatory effect on I_k. The results suggested that the molecular mechanisms of antihypertensive, heart rate slowing and β-receptor blocking effects of Bun might be due to decrease of I_ca and increase of I_k.

Keywords

levobunolol hydrochloride / ventricular myocyte / calcium channel current / potassium channel current

References

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