Cellular Participation in Atherogenesis: Selected Facets of Endothelium, Smooth Muscle, and the Peripheral Blood Monocyte

Abstract

An outside feature of continuous arterial endothelium is its barrier function, whereby the influx of plasma constituents into the arterial intima is regulated. Of particular importance is the observation that arterial endothelial permeability is topographically non-homogeneous, and that areas of spontaneously-differing permeability to plasma macromoleculas can be consistently identified in a number of species including pig, dog, and baboon (McGill et al. 1975; Packham et al. 1967; Bell et al. 1974a; Bell et al. 1974b; Sprague et al. 1980). Such areas of enhanced in vivo endothelial permeability, identified by their uptake of the protein-binding azo dye Evans Blue, are considered to be the sites of predilection for subsequent atheromatous development (McGill et al. 1957; Fry 1973; Schwartz et al. 1978). Because of the structural, hemodynamic, and functional implications of the Evans Blue model in atherogenesis, some of the salient features of these pre-lesion areas, characterized by the uptake of Evans Blue, are summarized in Table 1. Clearly, the aortic uptake of both ¹³¹I-albumin and ¹³¹I-fibrinogen at 2 hours is some 60% greater in blue than in white areas (Bell et al. 1974 a,b).