Journal
CTS-CLINICAL AND TRANSLATIONAL SCIENCE
Volume 1, Issue 2, Pages 126-133Publisher
WILEY-BLACKWELL
DOI: 10.1111/j.1752-8062.2008.00027.x
Keywords
adenosine receptors; Ca2+ transients; cardiac myocytes; heart failure; transgenic mice
Categories
Funding
- Pennsylvania Research Formulary Fund
- American Heart Association [SDG F64702]
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In the heart, adenosine binds to pharmacologically distinct G-protein-coupled receptors (A(1)-R, A(2A)-R, and A(3)-R). While the role of A(1)- and A(3)-Rs in the heart has been clarified, the effect of genetically manipulating the A(2A)-R has not been defined. Thus, we created mice overexpressing a cardiac-restricted A(2A)-R transgene. Mice with both low (Lo) and high (Hi) levels of A(2A)-R overexpression demonstrated an increase in cardiac contractility at 12 weeks. These changes were associated with a significantly higher systolic but not diastolic [Ca2+](i), higher maximal contraction amplitudes, and a significantly enhanced sarcoplasmic reticulum Ca2+ uptake activity. At 20 weeks, the effects of A(2A)-R overexpression on cardiac contractility diminished. The positive effects elicited by A(2A)-R overexpression differ from the heart failure phenotype we observed with A(1)-R overexpresson. Interestingly, coexpression of A(2A)-R TG(Hi), but not A(2A)-R TGLo, enhanced survival, prevented the development of left ventricular dysfunction and heart failure, and improved Ca2+ handling in mice overexpressing the A(1)-R. These results suggest that adenosine-mediated signaling in the heart requires a balance between A(1)- and A(2A)-Rs-a finding that may have important implications for the ongoing clinical evaluation of adenosine receptor subtype-specific agonists and antagonists for the treatment of cardiovascular diseases.
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