Structure and Mechanical Properties of Resistance Arteries in Hypertension

Abnormalities of resistance arteries may play a role in the pathogenesis and pathophysiology of hypertension in experimental animals and humans. Vessels that, when relaxed, measure <400 microm in lumen diameter act as the major site of vascular resistance and include a network of small arteries (lumen approximately 100 to 400 microm) and arterioles (<100 microm). Because increased peripheral resistance is generated by a narrowed lumen diameter, significant effort has been focused on determining the mechanisms that reduce lumen size. Three important vascular components are clearly involved, including alterations of vascular structure, mechanics (stiffness), and function. Structural abnormalities comprise a reduced lumen diameter and thickening of the vascular media, resulting in an increased media-lumen ratio. Changes in the mechanical properties of an artery, particularly increased stiffness, may also result in a reduced lumen diameter. These vascular abnormalities may be caused or influenced by the expression and/or topographic localization of extracellular matrix components, such as collagen and elastin, and by changes in cell-extracellular fibrillar attachment sites, such as adhesion molecules like integrins. This article discusses the abnormalities of resistance arteries in hypertension and reviews the evidence suggesting an important role for adhesive and extracellular matrix determinants.