| Background Calcium in cardiomyocytes is a dynamic yet delicate balance, handled by numerous calcium handling proteins. The process of influxing calcium ions and the transporting inner the cell is controlled by those proteins, some of which are located in the sarcolemma while others are in the membranes of sarcoplasmic reticulum. Calcium ions in plasmic not only effect the process of exciting-concentrition coupling, but also cause arrthymia, energy metabolism or as second message to activate kinds of cell proliferation, differentiation and function of oxidative phosphorylation. Two distinct types of voltage-dependent channels are now known to co-exist in the surface membranes of heart cell: L and T-type calcium channel. L-type calcium channel names for its large electric conductance and long-lasting channel opening, and it is also the major channel through which the Ca2+ ions influx into cells, while T-type calcium channel names for its tiny electric conductance and short-lasting channel opening. In the physiology condition, the T-type calcium channels are abundant in the fetal heart and during rapid growth in the early postnatal period. The density of T-type calcium current decreases rapidly soon after the birth in most of animals. In adult cardiomyocytes, the current is usually scarce or undetectable. But few animals like guinea pig still express this channel in atrial and ventricular cardiomyocytes. Previous studies reported resveratrol not only inhibits the ICa-L,but also decreased the INa, Iks, Iss, Ito in a concentration-dependent manner in the acute isolated guinea pig ventricular myocytes. These experiments generally display it can prolong action potential and effective refractory period, diminish the potential ventricular arrthymia. In order to futher investigate the possible mechanisms of resveratrol on inhibiting ventricular arrthymia and to understand its chronic effect on calcium current of guinea pig ventricular myocytes, we study the effects of resveratrol on the density of calcium current in cultured guinea pig ventricular myocytes using the whole-cell patch clamp technique.Objective To investigate the effects of resveratrol on the density of calcium current (ICa) in cultured guinea pig ventricular myocytes.Methods1. Single ventricular myocytes from adult male guinea pig weighing 250g～350g were isolated enzymatically using Langendorff-perfusion apparatus, seeded in the Petri dish and applied the resveratrol. Four groups were included: control group, low concentration group (RES 10μM), middle concentraton group (RES 30μM), high concentration group (RES 100μM).2. Using whole-cell patch clamp technique, to record the L-type and T-type calcium current respectively at different time.Results1. Effects of Resveratrol on the Density of L-type Calcium Current in Cultured Guinea Pig Ventricular Myocytes1) RES 30μM and RES 100μM decreased the density of ICa-L by 13 % and 27%, respectively, at 72h. There is a significant difference between RES 100μM and control (2.54±0.35 pA/pF vs. 3.48±0.42 pA/pF, P<0.05);2) RES 10μM, RES 30μM and RES 100μM inhibited the density of ICa-L in a time-dependent manner. RES 100μM significantly decreased ICa-L at 72h compared with that at 24h (2.54±0.35 pA/pF vs. 3.33±0.48 pA/pF, P<0.05).2. Effects of Resveratrol on the Density of T-type Calcium Current in Cultured Guinea Pig Ventricular Myocytes1) The density of the T-type calcium current was reduced by RES. RES100μM significantly inhibited ICa-T compared with control at 72h (2.61±0.64 10pA/pF vs. 4.79±0.67 10pA/pF, P<0.05).2) The same concentration of RES decreased the density of T-type calcium channel current in a time-dependent manner.ConclusionResveratrol has a tendency of inhibiting the density of calcium current in a time-dependent and concentration-dependent fashion. |
