Nitroglycerin and chromonar on small-vessel blood content of the ventricular walls.

WEISS, HARVEY R., AND MARTIN M. WINBURY. Nitroglycerin and chromonar on small-vessel blood content of the ventricular walls. Am. J. Physiol. 226(4) : 838-843. 1974.-The small-vessel blood content of the ventricular walls in anesthetized dogs was determined with 5gFe-siderophilin-labeled plasma. In the control state, the right ventricle (RV) contained 7.62 ml blood/l00 g tissue, the septum 8.17, and the left ventricle (LV) 9.69. The deep regions of LV contained more blood than the superficial regions; the apexes of all regions had a higher blood content than the bases. Seven to nine minutes after the intravenous administration of 20 pg/kg of nitroglycerin, the small-vessel blood content of the heart was slightly, but not significantly reduced. The transmural gradient of the LV was not altered significantly. Twenty minutes after chromonar, 7.5 mg/kg, the small-vessel blood content was not significantly altered, and the gradient between the superficial and deep layers was unchanged. Asphyxia significantly increased the small-vessel blood content of all regions of the myocardium, indicating a reserve of unopened capillaries. It is assumed that the gradients in blood content are representative of gradients in opencapillary density within the ventricular walls.