Arteriolar and Capillary Tissue Supply Areas in Myocardium

Abstract

The principal role of the mammalian coronary microcirculation is to provide oxygen to the working heart. Terminal arteries and arterioles regulate coronary nutritive blood flow and the capillary net provides the structural basis for oxygen transport by the process of diffusion. Most of our previous research has focussed on the predominant component of the microvascular bed, namely, coronary capillaries. In this connection, the amount of tissue supplied by individual coronary capillaries and the variability of capillary spacing have been found to constitute two of the principal oxygen determinants (Turek et al., 1991). Both may be derived from measuring the size of individual capillary domains, defined as tissue cross-sectional areas closer to a given capillary than to any other. As the distribution of these domain areas is log-normal, the standard deviation of this distribution (SDlog) best serves as a heterogeneity index of capillary spacing. Our established histochemical method (Batra et al., 1989) has previously been used to provide color distinction within capillary regions: proximal capillary portions i.e., close to feeding arterioles having larger capillary domains stain blue, while those within distal capillary regions and with smaller domain areas stain red. Despite widespread acceptance of our technique, some reservation has nevertheless been put forward as to the validity of this approach in distinguishing unambiguously separate capillary regions.