title: Role of adenosine in regulating the heterogeneity of skeletal muscle blood flow during exercise in humans.
abstract: Evidence from both animal and human studies suggests that adenosine plays a role in the regulation of exercise hyperemia in skeletal muscle. We tested whether adenosine also plays a role in the regulation of blood flow (BF) distribution and heterogeneity among and within quadriceps femoris (QF) muscles during exercise, measured using positron emission tomography. In six healthy young women, BF was measured at rest and then during three incremental low and moderate intermittent isometric one-legged knee-extension exercise intensities without and with theophylline-induced nonselective adenosine receptor blockade. BF heterogeneity within muscles was calculated from 16-mm(3) voxels in BF images and heterogeneity among the muscles from the mean values of the four QF compartments. Mean BF in the whole QF and its four parts increased, and heterogeneity decreased with workload both without and with theophylline (P < 0.001). Adenosine receptor blockade did not have any effect on mean bulk BF or BF heterogeneity among the QF muscles, yet blockade increased within-muscle BF heterogeneity in all four QF muscles (P = 0.03). Taken together, these results show that BF becomes less heterogeneous with increasing exercise intensity in the QF muscle group. Adenosine seems to play a role in muscle BF heterogeneity even in the absence of changes in bulk BF at low and moderate one-leg intermittent isometric exercise intensities.
authors: Turku PET Centre, FIN-20521, Turku, Finland. ilkka.heinonen@tyks.fi
authors: Ilkka
authors: I
authors: Heinonen
authors: Sergey V
authors: SV
authors: Nesterov
authors: Jukka
authors: J
authors: Kemppainen
authors: Pirjo
authors: P
authors: Nuutila
authors: Juhani
authors: J
authors: Knuuti
authors: Ruut
authors: R
authors: Laitio
authors: Michael
authors: M
authors: Kjaer
authors: Robert
authors: R
authors: Boushel
authors: Kari K
authors: KK
authors: Kalliokoski
mesh_terms: D000241:Adenosine / Q000378:metabolism*; D000328:Adult; D001783:Blood Flow Velocity; D001794:Blood Pressure; D015444:Exercise / Q000502:physiology*; D005260:Female; D006339:Heart Rate; D006801:Humans; D007262:Infusions, Intravenous; D007537:Isometric Contraction; D049268:Positron-Emission Tomography; D058915:Purinergic P1 Receptor Antagonists; D052097:Quadriceps Muscle / Q000098:blood supply* / Q000000981:diagnostic imaging / Q000187:drug effects / Q000378:metabolism*; D018047:Receptors, Purinergic P1 / Q000378:metabolism*; D012039:Regional Blood Flow; D013806:Theophylline / Q000008:administration & dosage
chemical_list: D058915:Purinergic P1 Receptor Antagonists; D018047:Receptors, Purinergic P1; D013806:Theophylline; D000241:Adenosine