Altered structure and distensibility of arteries in salt-fed rats.

Abstract

Habitual high-sodium diet may cause stiffening of arteries. The aim of this study was to investigate the long-term effects of physiologically relevant high-sodium diet on the structure and distensibility of arteries in rats. Adult male Sprague-Dawley rats were fed 2% NaCl diet for 3 or 6 months; rats fed 0.7% NaCl diet were controls. Pressure-volume (distensibility) relationships were measured in the presence and absence of calcium in excised, in-vitro perfused segments of right carotid artery and of second order mesenteric arteries. The left carotid artery and the remaining mesenteric arteries of rats were perfused in situ with papaverine followed by fixative at 100 mmHg, and then embedded in epoxy for morphometric measurements. The tail systolic blood pressure (SBP), and in subgroups of rats, the directly measured mean arterial pressure (MAP), of salt-fed rats at 3 and 6 months were unchanged. At 3 months, there was dilatation (increased lumen area) of both carotid and mesenteric arteries of salt-fed rats, without a change in distensibility. At 6 months, the lumen area of carotid arteries of salt-fed rats returned to control value (inward remodeling), and carotid artery distensibility remained unchanged. At 6 months, there was further dilatation (P <0.01) and reduced distensibility (P =0.01) of mesenteric arteries in salt-fed rats. A three-fold increase in dietary sodium intake leads to dilatation of arteries in normotensive rats. When there is compensatory remodeling, the distensibility of arteries remains unchanged; when compensation is lacking, unopposed dilatation is associated with reduced distensibility.