The effects of intracoronary injection of nitroglycerin, pentaerythritol trinitrate and dipyridamole on subepicardial (epi) and subendocardial (endo) oxygen tension were compared in anaesthetized open chest dogs. The PO2 was determined simultaneously at a depth of 3 mm (epi) and 9 mm (endo) below the surface of the left ventricle with small platinum electrodes by a polarographic method. The two nitrates produced a selective increase in endo PO2, no change in epi PO2 and a transient increase in coronary blood flow. In some cases, endo PO2 increased in the absence of a significant rise in blood flow. Dipyridamole consistently caused a prolonged increase in coronary flow; epi PO2 increased slightly and endo PO2 decreased in some of the animals. Using data for nitroglycerin on PO2, regional blood flow and intercapillary distance, the changes in metabolism were predicted on the basis of the Krogh analysis. Metabolism was reduced in both epi and endo; PO2 and blood flow were increased in endo and decreased in epi, and intercapillary distances were unchanged. It is concluded that the nitrates increase endo PO2 of the left ventricle by a decrease in metabolism and redistribution of blood flow to endo from epi.
All Science Journal Classification (ASJC) codes
- Cardiology and Cardiovascular Medicine
- Cell Biology