Amount and distribution of Rb-86 transported into myocardium from ventricular lumen

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Abstract
The left coronary arteries of dogs were perfused with unlabeled blood while Rb86- and Cr51 -tagged erythrocytes were administered systemically. Perfusion rate was continuously adjusted to maintain mean coronary and arotic pressures equal. The extravascular Rb&6 content of the entire left ventricle would have been provided by 4% of mean coronary blood flow, indicating that transport from the lumen is not important for the over-all nutrition of the unstressed heart. Luminal blood is, however, a major source of supply for the deep spiral and papillary muscles; the average Rb86 content of the innermost 2 mm was equivalent to a coronary blood flow of 25 ml/100 g/min. Significant amounts of extravascular Rb86 were detected as much as 10 mm from the lumen. Evidence is offered for the view that both diffusion from endocardial surfaces and transport by luminal vessels contributed to Rb86 uptake. The functional significance of a luminal blood supply to the innermost fibers is discussed in relation to transmural gradients of coronary blood flow and tissue O2 tension.