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To examine the role of nitric oxide in the β-adrenergic vasodilation of epicardial coronary arteries in dogs, 12 dogs were instrumented for measurement of left anterior descending coronary artery diameter by transthoracic echocardiography before and after dobutamine (5 μg/kg/min IV) with and without intracoronary infusion of N G-monomethyl-L-arginine (L-NMMA) (1 mg/kg). In all 12 dogs, the diameter of left anterior descending coronary artery increased significantly from 2.35±0.25 mm to 2.59±0.24 mm (P<0.001) after dobutamine administration. In 6 of the 12 dogs, the percent change in left anterior descending coronary artery diameter induced by dobutamine decreased significantly from 12.5%±8.6% to -1.5%±5.4% (P<0.05) after the administration of intracoronary L-NMMA (1 mg/kg for 5 min) to block nitric oxide synthesis from L-arginine. The study demonstrated that nitric oxide formation contributes to the β-adrenergic dilatory response of epicardial coronary arteries to dobutamine in dogs.
To examine the role of nitric oxide in the β-adrenergic vasodilation of epicardial coronary arteries in dogs, 12 dogs were instrumented for measurement of left anterior descending coronary artery diameter by transthoracic echocardiography before and after dobutamine (5 μg / kg / min IV) with and without intracoronary infusion of N G-monomethyl-L-arginine (L-NMMA) (1 mg / kg) In all 12 dogs, the diameter of left anterior descending coronary artery increased significantly from 2.35 ± 0.25 mm to 2.59 ± 0.24 mm (P <0.001) after dobutamine administration. In 6 of the 12 dogs, the percent change in left anterior descending coronary artery diameter induced by dobutamine decreased significantly from 12.5% ± 8.6% to -1.5% ± 5.4% (P <0.05) after the administration of intracoronary L-NMMA (1 mg / kg for 5 min) to block nitric oxide synthesis from L-arginine. The study demonstrated that nitric oxide formation contributes to the β-adrenergic dilatory response of epicardial coronary arteries to dobutamine in dogs.