Greater adenosine A(2A) receptor densities in cardiac and skeletal muscle in endurance-trained men: a [C-11]TMSX PET study
ABSTRACT We examined the densities of adenosine A(2A) receptors in cardiac and skeletal muscles between untrained and endurance-trained subjects using positron emission tomography (PET) and [7-methyl-11C]-(E)-8-(3,4,5-trimethoxystyryl)-1,3,7-trimethylxanthine ([11C]TMSX), a newly developed radioligand for mapping adenosine A(2A) receptors. Five untrained and five endurance-trained subjects participated in this study. The density of adenosine A(2A) receptors was evaluated as the distribution volume of [11C]TMSX in cardiac and triceps brachii muscles in the resting state using PET. The distribution volume of [11C]TMSX in the myocardium was significantly greater than in the triceps brachii muscle in both groups. Further, distribution volumes [11C]TMSX in the trained subjects were significantly grater than those in untrained subjects (myocardium, 3.6+/-0.3 vs. 3.1+/-0.4 ml g(-1); triceps brachii muscle, 1.7+/-0.3 vs. 1.2+/-0.2 ml g(-1), respectively). These results indicate that the densities of adenosine A(2A) receptors in the cardiac and skeletal muscles are greater in the endurance-trained men than in the untrained men.
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ABSTRACT: [(11)C]TMSX ([7-N-methyl-(11)C]-(E)-8-(3,4,5-trimethoxystyryl)-1,3,7-trimethylxanthine) is a selective adenosine A2A receptor (A2AR) radioligand. In the central nervous system (CNS), A2AR are linked to dopamine D2 receptor function in striatum, but they are also important modulators of inflammation. The golden standard for kinetic modeling of brain [(11)C]TMSX positron emission tomography (PET) is to obtain arterial input function via arterial blood sampling. However, this method is laborious, prone to errors and unpleasant for study subjects. The aim of this work was to evaluate alternative input function acquisition methods for brain [(11)C]TMSX PET imaging. First, a noninvasive, automated method for the extraction of gray matter reference region using supervised clustering (SCgm) was developed. Second, a method for obtaining a population-based arterial input function (PBIF) was implemented. These methods were created using data from 28 study subjects (7 healthy controls, 12 multiple sclerosis patients, and 9 patients with Parkinson's disease). The results with PBIF correlated well with original plasma input, and the SCgm yielded similar results compared with cerebellum as a reference region. The clustering method for extracting reference region and the population-based approach for acquiring input for dynamic [(11)C]TMSX brain PET image analyses appear to be feasible and robust methods, that can be applied in patients with CNS pathology.Journal of Cerebral Blood Flow & Metabolism advance online publication, 5 November 2014; doi:10.1038/jcbfm.2014.194.Journal of Cerebral Blood Flow & Metabolism 11/2014; 35(1). DOI:10.1038/jcbfm.2014.194 · 5.34 Impact Factor
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ABSTRACT: The adenosine A2A receptor (A2AR) is highly concentrated in the striatum, and a therapeutic target for Parkinson's disorder (PD) and Huntington's disease. High affinity and selective radiolabeled A2AR antagonists can be important research and diagnostic tools for PD. Positron Emission Tomography (PET) can play an important role by measuring radiolabeled A2A antagonists non-invasively in the brain. However, till date no complete review on A2AR PET ligands is available. The present article is therefore focused on available PET tracers for A2AR and their detailed biological evaluation in rodents, nonhuman primates and humans. Drug design and development by molecular modeling is discussed including new lead structures which are potential candidates for radiolabeling and mapping of cerebral A2ARs. A brief overview of functions of adenosine in health and disease, including the relevance of A2AR for PD has also been presented.Current Medicinal Chemistry 09/2013; DOI:10.2174/09298673113206660265 · 3.72 Impact Factor