Function of SERCA2a Ca ²⁺ pump is unchanged in cTnI-ND,Tnni3 ^−/− mouse hearts. (A) The SDS-PAGE gel and Western blot show high level expression of SERCA2a in mouse heart and slow fiber-rich soleus muscle but not in fast fiber type extensor digitorum longus (EDL) muscle, which was decreased in the Gsα knockout (Gsα-KO) failing heart control (Feng et al., 2008b). Densitometry quantification normalized to actin showed that the levels of SERCA2a were not significantly different in cTnI-ND,Tnni3^−/− and WT hearts. (B) The Western blots show the expected expression of phospholamban (PLB), a regulator of SERCA2a, in mouse heart but not in skeletal muscles and the increased phosphorylation of PLB when ex vivo mouse working hearts were treated with 10 nM ISO. β-adrenergic defective Gsα-KO mouse heart was used as a negative control. Densitometry quantification normalized to actin showed similar levels of total PLB expression and phosphorylation upon ISO treatment in cTnI-ND,Tnni3^−/− and WT hearts. Values are mean ± SEM. n = 5 mice each in WT and cTnI-ND,Tnni3^−/− groups. Statistical analysis was performed using Student’s t test, and no significant difference was found. MHC, myosin heavy chain.