| Objective:To explore possible electrophysiological mechanisms of single atrial myocyte by evaluating the effects of angiotensinⅡ(AngⅡ) and telmisartan on transient outward potassium currents(Ito) and L-type calcium currents (ICa-L) in Sprague-Dawley rats.Methods:Single atrial myocyte of SD rats was obtained by enzymatic dissociation method. The whole cell patch-clamp recording technique was used to record the change of Ito and ICa-L by intervening of AngⅡ, telmisartan and AngⅡplus telmisartan respectively. Experimental groups:⑴AngⅡgroup: cells were perfused with bath solution containing AngⅡ(0.1μmol/L);⑵Telmisartan group: cells were perfused with bath solution containing telmisartan (0.01μmol/L);⑶Combined group, myocytes were perfused with bath solution containing AngⅡ(0.1μmol/L) and telmisartan (0.01μmol/L).Results : Compared with baseline value, AngⅡ(0.1μmol/L), Telmisartan(0.01μmol/L) and AngⅡplus Telmisartan group significantly decreased the peak density of Ito in SD rat atrial myocytes (22.48±2.75 vs. 15.71±2.06 pA/pF, P<0.01), (24.16±2.36 vs. 16.15±1.82 pA/pF, P<0.01) and (24.41±2.27 vs. 21.35±1.46 pA/pF, P<0.05) respectively. AngⅡ(0.1μmol/L) significantly increased the peak density of ICa-L in SD rat atrial myocytes (-4.51±0.38 vs. -5.16±0.29 pA/pF, P<0.01). Telmisartan (0.01μmol/L) had no significant effects on ICa-L in the rat atrial myocytes (-4.35±0.27 vs. -4.29±0.34 pA/pF, P>0.05), but it could antagonize the effects of AngⅡ. In the AngⅡcombined telmisartan group, the peak density of ICa-L was(-4.08±0.28 vs. -4.20±0.31 pA/pF, P>0.05), which was significantly different from that of AngⅡgroup (P<0.05).Conclusion:AngⅡand telmisartan had directly electrophysiological effects on SD rat atrial myocytes as well as telmisartan had antagonist effects on AngⅡat the level of angiotensin receptor.
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