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.