US EPA

1784648 

Journal Article 

Effect of Nitroglycerin on Total and Regional Coronary Blood Flow in The Normal and Ischaemic Canine Myocardium 

Mathes, P; Rival, J 

1971 

Yes 

Cardiovascular Research
ISSN: 0008-6363
EISSN: 1755-3245 

NIOSH/00130467 

5 

1 

54-61 

The effect of nitroglycerin (55630) (TNG) on total coronary flow and its regional distribution in normal and ischemic myocardium was studied in dogs. Fractional extraction of rubidium-86 (Rb-86) was used for estimation of the regional distribution of coronary flow. Total coronary flow was estimated by the use of an electromagnetic flowmeter. Adult mongrel-dogs were catheterized into the superior and inferior vena cava and descending aorta for the administration of drugs and recording of aortic pressure, respectively. Following thoracotomy, flow probes were placed around the circumflex coronary artery and the left descending artery. TNG was injected intravenously at 5 micrograms per kilogram (microg/kg) into normal dogs, those with partial occlusion of the left circumflex and descending coronary arteries, and those with impaired circulation given a continuous intravenous infusion of noradrenaline-bitartrate (51401) at 0.5microg/kg. Results were compared to dogs without drug treatment, dogs with noradrenaline infusion only, and dogs with noradrenaline and induced ischemia. Fifteen seconds after TNG injection, a marked increase of approximately 66 percent occurred in coronary flow in normal dogs, lasting for about 20 seconds. Rb-86 uptake of subendocardial layers was slightly decreased. In ischemic dogs, perfusion of the left ventricle was decreased; systolic and diastolic blood pressures were markedly reduced, reducing intramyocardial tissue pressure. Noradrenaline alone increased blood pressures to an average of 162/112 compared with a control value of 119/86, but subendocardial perfusion remained normal. Ischemic animals perfused with noradrenaline had a lower capillary flow in the inner than the outer myocardial layers. Ischemic animals perfused with noradrenaline and treated with TNG showed changes in total coronary flow and blood pressure similar to those in normal animals. A significant increase in Rb-86 uptake in subendocardial layers occurred. The authors conclude that TNG must have reduced elevated intraventricular and intramyocardial tissue pressure which may have been sufficient to restore normal flow to the endocardium. 

DCN-118945; Animal studies; Nitrates; Chemical properties; Dose response; Blood analysis; Myocardial disorders; Physiological response; Drug interaction; Biological factors