Effects of wenxin keli on the action potential and L-type calcium current in rats with transverse aortic constriction-induced heart failure

Abstract

Objective. We investigated the effects of WXKL on the action potential (AP) and the L-type calcium current (I Ca-L) in normal and hypertrophied myocytes. Methods. Forty male rats were randomly divided into two groups: the control group and the transverse aortic constriction- (TAC-) induced heart failure group. Cardiac hypertrophy was induced by TAC surgery, whereas the control group underwent a sham operation. Eight weeks after surgery, single cardiac ventricular myocytes were isolated from the hearts of the rats. The APs and I Ca-L were recorded using the whole-cell patch clamp technique. Results. The action potential duration (APD) of the TAC group was prolonged compared with the control group and was markedly shortened by WXKL treatment in a dose-dependent manner. The current densities of the I Ca-L in the TAC group treated with 5 g/L WXKL were significantly decreased compared with the TAC group. We also determined the effect of WXKL on the gating mechanism of the I Ca-L in the TAC group. We found that WXKL decreased the I Ca-L by accelerating the inactivation of the channels and delaying the recovery time from inactivation. Conclusions. The results suggest that WXKL affects the AP and blocked the I Ca-L, which ultimately resulted in the treatment of arrhythmias.

Figure 1

(a) Preparation of the hearts from the control group (a1) and the TAC group (a2). (b) Left ventricular apical biopsy of the control group ((b1), HE staining 400x magnification) and the TAC group ((b2), HE staining 400x magnification). (c) Pathological section of the largest cross-section of the control group (c1) and the TAC group (c2). (d) Single ventricular myocytes from the control group (d1) and the TAC group (d2). (e) Typical echocardiography images from the control group (e1) and the TAC group (e2). Eight weeks after the TAC surgery, the cardiac structure and function were measured through echocardiography. We evaluated the cardiac systolic and diastolic functions by measuring the left ventricular posterior wall thickness (LPWD) of the control group and the TAC group (c3). **P < 0.01 versus the control group.

Figure 2

Representative AP traces recorded from the control and the TAC group and effects of different concentrations of WXKL on the APs in the TAC group. (a) APs of the control group and the TAC group. (b) APD₂₀, APD₅₀, and APD₉₀ of the control group and the TAC group. (c) Effects of 1, 5, and 10 g/L WXKL on the APs in the TAC group. (d) APD₂₀, APD₅₀, and APD₉₀ of the TAC group after treatment with 1, 5, and 10 g/L WXKL. *P < 0.05 and **P < 0.01 versus the control group. ^Δ P < 0.05 and ^ΔΔ P < 0.01 versus the TAC group.

Figure 3

Effects of WXKL on the I _Ca-L in the control group. (a) Effects of 1, 5, and 10 g/L WXKL on the I _Ca-L in the control group. After treatment with WXKL, the current amplitudes of the control group were significantly reduced. (b) Concentration-dependent effects of WXKL on the I _Ca-L in the control group (IC₅₀ = 6.23 g/L). (c) Time-dependent effects of 5 g/L WXKL on the I _Ca-L in the control group. *P < 0.05 and **P < 0.01 versus the control group.

Figure 4

Effects of WXKL on the I _Ca-L in the TAC group. (a) Representative I _Ca-L traces recorded from the control group. (b) Representative I _Ca-L traces recorded from the TAC group. (c) Representative I _Ca-L traces recorded from the TAC group in the presence of 5 g/L WXKL. (d) The peak current density-voltage relationship showed that the current densities in the TAC group were significantly increased by a range of −10 mV to +10 mV, and the current densities in the TAC group after treatment with 5 g/L WXKL were significantly reduced by a range of −10 mV to +40 mV. (e) The peak current densities in each group exhibited significant differences. ((f) and (g)) Representative I _Ca-L traces recorded from the control group and after treatment with 5 g/L WXKL. *P < 0.05 and **P < 0.01 versus the control group. ^Δ P < 0.05 and ^ΔΔ P < 0.01 versus the TAC group.

Figure 5

Effects of WXKL on the steady-state activation and inactivation kinetics of the I _Ca-L in the TAC group. (a) Steady-state activated curve of the control group, the TAC group and the TAC group treated with 5 g/L WXKL. The steady-state activation curve of each group did not exhibit significant differences. (b) The V _1/2,act of each group did not exhibit significant differences. (c) The k _act of each group did not exhibit significant differences. (d) The steady-state inactivation curve of the TAC group was shifted to a more negative potential, whereas the steady-state inactivation curve of the TAC group treated with 5 g/L WXKL was shifted to a more active potential. (e) The V _1/2,inact in each group exhibited significant differences. (f) The k _inact of each group exhibited significant differences. *P < 0.05 and **P < 0.01 versus the control group. ^Δ P < 0.05 and ^ΔΔ P < 0.01 versus the TAC group.

Figure 6

Effects of WXKL on the recovery of the I _Ca-L from inactivation in the TAC group. The time course of the recovery from inactivation was fitted with a single exponential function. The recovery from inactivation of the I _Ca-L was changed after exposure to 5 g/L WXKL.