FIGURE 2.

(A,B) cAMP content in isolated ventricular cardiomyocytes from WT and A_2A-AR-overexpressing animals. cAMP content was determined by Biotrak direct Enzymimmunoassay. Note concentration dependent increase of cAMP content by A_2A-AR agonist CGS 21680 in A_2A-AR cardiomyocytes (A); this effect could be completely blocked by A_2A-AR antagonist ZM 241385. The effect of β-adrenoceptor agonist isoproterenol on cAMP content did not differ between WT and A_2A-AR (B). (C,D) Phosphorylation of phospholamban at serine-16 (pPLB). (E,F) Phosphorylation of the inhibitory subunit of troponin (pTnI). The phosphorylation state of PLB and TnI was assessed by phosphorylation specific antibodies. The signals obtained using phosphorylation specific antibodies were normalized to the corresponding protein expression. Note concentration dependent increase of pPLB (C) and pTnI (E) by A_2A-AR agonist CGS 21680 in A_2A-AR cardiomyocytes; these effects were abolished by A_2A-AR antagonist ZM 241385. The effects of isoproterenol on protein phosphorylation were comparable in WT and A_2A-AR (D,F). ^⋆p < 0.05 vs. Ctr; ^#p < 0.05 vs. WT.