Cell Volume Regulation and Vascular Endothelial Function

Abstract

In the vasculature, the endothelium consists of a single monolayer that forms an interface between the blood and the underlying vessel and tissue. Accordingly, it has specialized functions that are critical to normal vascular function. Most apparent is its role as a physical barrier. Endothelial injury with subsequent exposure of subendothelial matrix may be important in the genesis of a variety of thrombotic disorders. Endothelial denudation may be an early event in atherosclerosis, resulting in platelet activation, release of platelet-derived growth factor, and eventual migration and proliferation of smooth muscle cells in the intima (Ross 1986). In addition to being a physical barrier, endothelium is a selective permeability barrier, allowing passage of nutrients and restricting passage of macromolecules. This is particularly important in the cerebral vasculature, where endothelium forms the blood-brain barrier (Janzer and Raff 1987), and in the renal glomerulus, where endothelium contributes to the ultrafiltration barrier. Endothelium also has important paracrine functions in blood vessels that allow it to regulate platelet and leukocyte function, on the one hand, and vascular smooth muscle tone, on the other (Vane et al. 1990). Through these various properties the endothelium plays a critical role in governing thrombosis, inflammation, and hemodynamics.