Effects of Total Flavones from Acanthopanax senticosus on L‐type Calcium Channels,Calcium Transient and Contractility in Rat Ventricular Myocytes

Acanthopanax senticosus (Rupr. et Maxim.) Harms (AS), a traditional herbal medicine, has been widely used to treat ischemic heart disease. However, the underlying cellular mechanisms of its benefits to cardiac function remain unclear. The present study examined the effects of total flavones from AS (TFAS) on L‐type Ca²⁺ channel currents (I_Ca‐L) using the whole cell patch‐clamp technique and on intracellular calcium ([Ca²⁺]_i) handling and cell contractility in rat ventricular myocytes with the aid of a video‐based edge‐detection system. Exposure to TFAS resulted in a concentration‐ and voltage‐dependent blockade of I_Ca‐L, with the half‐maximal inhibitory concentration (IC₅₀) of 283.12 µg/mL and the maximal inhibitory effect of 36.49 ± 1.95%. Moreover, TFAS not only increased the maximum current in the current–voltage relationship but also shifted the activation and inactivation curves of I_Ca‐L toward the hyperpolarizing direction. Meanwhile, TFAS significantly reduced amplitudes of myocyte shortening and [Ca²⁺]_i with an increase in the time to 10% of the peak (Tp) and a decrease in the time to 10% of the baseline (Tr). Thus, the cardioprotective effects of TFAS may be attributed mainly to the attenuation of [Ca²⁺]_i through the direct inhibition of I_Ca‐L in rat ventricular myocytes and consequent negative effect on myocardial contractility. Copyright © 2015 John Wiley & Sons, Ltd.     

New Findings on the Effects of Tannic Acid: Inhibition of L‐Type Calcium Channels,Calcium Transient and Contractility in Rat Ventricular Myocytes

Tannic acid (TA) is a group of water‐soluble polyphenolic compounds that occur mainly in plant‐derived feeds, food grains and fruits. Many studies have explored its biomedical properties, such as anticancer, antibacterial, antimutagenic, antioxidant, antidiabetic, antiinflammatory and antihypertensive activities. However, the effects of TA on the L‐type Ca²⁺ current (I_Ca‐L) of cardiomyocytes remain undefined. The present study examined the effects of TA on I_Ca‐L using the whole‐cell patch‐clamp technique and on intracellular Ca²⁺ handling and cell contractility in rat ventricular myocytes with the aid of a video‐based edge detection system. Exposure to TA resulted in a concentration‐ and voltage‐dependent blockade of I_Ca‐L, with the half maximal inhibitory concentration of 1.69 μM and the maximal inhibitory effect of 46.15%. Moreover, TA significantly inhibited the amplitude of myocyte shortening and peak value of Ca²⁺ transient and increased the time to 10% of the peak. These findings provide new experimental evidence for the cellular mechanism of action of TA and may help to expand clinical treatments for cardiovascular disease. Copyright © 2016 John Wiley & Sons, Ltd.