Greater adenosine A(2A) receptor densities in cardiac and skeletal muscle in endurance-trained men: a [11C]TMSX PET study.
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.
Mizuno
Masaki
M
Faculty of Sport Sciences, Waseda University, Tokorozawa, Saitama 359-1192, Japan.
Kimura
Yuichi
Y
Tokizawa
Ken
K
Ishii
Kenji
K
Oda
Keiichi
K
Sasaki
Toru
T
Nakamura
Yoshio
Y
Muraoka
Isao
I
Ishiwata
Kiichi
K
D000328:Adult; D006321:Heart / Q000000981:diagnostic imaging / Q000502:physiology*; D006801:Humans; D018482:Muscle, Skeletal / Q000000981:diagnostic imaging / Q000502:physiology*; D009928:Organ Specificity; D010807:Physical Endurance / Q000502:physiology*; D010809:Physical Fitness / Q000502:physiology*; D049268:Positron-Emission Tomography / Q000379:methods; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D043705:Receptor, Adenosine A2A / Q000378:metabolism*; D014018:Tissue Distribution; D014970:Xanthines / Q000493:pharmacokinetics*
C405422:KF18446; D019275:Radiopharmaceuticals; D043705:Receptor, Adenosine A2A; D014970:Xanthines