Institution: | aFaculty of Sport Sciences, Waseda University, Tokorozawa, Saitama 359-1192, Japan bPositron Medical Center, Tokyo Metropolitan Institute of Gerontology, Itabashi-ku, Tokyo 173-0022, Japan cGraduate School of Human Sciences, Waseda University, Tokorozawa, Saitama 359-1192, Japan |
Abstract: | We examined the densities of adenosine A2A 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 A2A receptors. Five untrained and five endurance-trained subjects participated in this study. The density of adenosine A2A 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 A2A receptors in the cardiac and skeletal muscles are greater in the endurance-trained men than in the untrained men. |