Reversible phosphorylation governed by kinases and phosphatases is a crucial post-translational modifications of the protein functions. Dysregulation of protein phosphorylation has been linked to a host of dysfunctional and arrhythmic heart diseases(1, 2). We have previously observed that the mice with cardiac-tagerted deletion of Cα subunit of PP2A (KO) generated with C57BL/6J mice by Gu et al(3), developed dilated cardiomyopathy at the postnantal day 11 and died around the day 13. The goal of present study was to analyse patterns of cardiac electrical remodeling in KO mice. The mice at 9 to 11 days after birth were anaesthetised with avertin (240 mg/Kg, i.p.) or phenobarbitol sodium (40mg/Kg, i.p.) for echocardiographic meaurements (n=3 respectively, for each group) or for the heart dessection. Values are means ± S.E.M, compared by Student’s paired t.-test or ANOVA followed by a q. test. As compared to control, cardiac hypertrophy was evidenced by the increases in left ventricle to body weight ratio and left ventricle mass, by the significant elevation of mRNA expression for ANP, BNP and β-MHC, by the increase in both end of diastolic and end of systolic volumes for left ventricles as well as by the decrease in the fractional shortening and ejection fraction in KO mice (P<0.05). In addition to morphological changes observed in HE staining, notable ultrastructural alterations in KO myocytes were illustrated in TEM analysis. Moreover, electriophysiological recordings indicated that the duration of APs in KO myocytes were markedly prolonged as compared with those in control (P<0.01 KO vs control, n=9 and 7 cells, respectively, from at least 3 to 4 mice for each group). In contrast, no changes were observed in RPs and other parameters of APs. Consequently, a significant reduction of transient outward K+ currents and intermediate increase of L-type Ca2+ currents were documented in KO myocytes (P<0.05 KO vs control, n=7 and 5 respectively). In consistence with changes in ion currents, an upregulation of Cav1.2, whereas down-regulations of Kv4.2, Kv4.3, Kv1.4 and KChIP2 proteins co-accembling α and β subunites of transient outward K+ channel were detected by western blot analysis (from 3 independent expreiments). Importantly, the increased phosphorylation of Cav1.2 Ca2+ channels in KO mice was demonstrated by immunohistochemistry and western blot analysis in comparasion with those of control (n=3 for each, P<0.05). Taken together, these findings are indicative of the fundamental role of PP2A in the mouse heart and imply that loss of PP2A may disturbant Cav1.2 phosphorylation and intracellular Ca2+ concentration and then, causes cardiomyopathy along with electrical remodeling.