Microcirculation17(8), 600–607. This study was designed to elucidate the contribution of adenosine A2A and A2B receptors to

coronary reactive hyperemia and downstream K+ channels involved. Coronary blood flow was measured in open-chest anesthetized dogs. Adenosine dose-dependently increased coronary flow from 0.72 ± 0.1 to 2.6 ± 0.5 mL/minute/g under control conditions. Inhibition of selleck chemicals llc A2A receptors with SCH58261 (1 μm) attenuated adenosine-induced dilation by ∼50%, while combined administration with the A2B receptor antagonist alloxazine (3 μm) produced no additional effect. SCH58261 significantly reduced reactive hyperemia in response to a transient 15 second occlusion; debt/repayment ratio decreased from 343 ± 63 to 232 ± 44%. Alloxazine alone attenuated adenosine-induced increases in coronary blood flow by ∼30% but failed to alter reactive hyperemia. check details A2A receptor agonist CGS21680 (10 μg bolus) increased coronary blood flow by 3.08 ± 0.31 mL/minute/g. This dilator response was attenuated

to 0.76 ± 0.14 mL/minute/g by inhibition of KV channels with 4-aminopyridine (0.3 mm) and to 0.11 ± 0.31 mL/minute/g by inhibition of KATP channels with glibenclamide (3 mg/kg). Combined administration abolished vasodilation to CGS21680. These data indicate that A2A receptors contribute to coronary vasodilation in response to cardiac ischemia via activation of KV and KATP channels. “
“There is a debate if the [NO] required to influence vascular smooth muscle is below 50 nM or much higher. Electrodes with 30 μm and larger diameter report [NO] below 50 nM, whereas those with diameters of <10–12 μm Bupivacaine report hundreds of nM. This study examined how size of electrodes influenced

[NO] measurement due to NO consumption and unstirred layer issues. Electrodes were 2 mm disk, 30 μm × 2 mm carbon fiber, and single 7 μm diameter carbon fiber within open tip microelectrode, and exposed 7 μm carbon fiber of ~15 μm to 2 mm length. All electrodes demonstrated linear calibrations with sufficient stirring. As stirring slowed, 30 μm and 2 mm electrodes reported much lower [NO] due to unstirred layers and high NO consumption. The three 7 μm microelectrodes had minor stirring issues. With limited stirring with NO present, 7 μm open tip microelectrodes advanced toward 30 μm and 2 mm electrodes experienced dramatically decreased current within 10–50 μm of the larger electrodes due to high NO consumption. None of the 7 μm microelectrodes interacted. The data indicate large electrodes underestimate [NO] due to excessive NO consumption under conditions where unstirred layers are unavoidable and true microelectrodes are required for valid measurements. “
“In skeletal muscle, growth of capillaries is an important adaptation to exercise training that secures adequate diffusion capacity for oxygen and nutrients even at high-intensity exercise when increases in muscle blood flow are profound.