Sodium Intake, Large Artery Stiffness, and Proteoglycans in the Spontaneously Hypertensive Rat

Abstract

Although the role of sodium in hypertension has been documented extensively, its effect on large arteries has not been well documented. We examined the effect of high-sodium (8%) diet and the diuretic indapamide (IND) on systemic hemodynamics and aortic wall structure and composition in collagen, elastin, and hyaluronan. Four groups of spontaneously hypertensive rats (SHR) were studied after 8 weeks: those on a normal diet (SHR), a high-sodium diet (SHR+NaCl), a normal diet with IND (SHR+IND), and a high-sodium diet with IND (SHR+NaCl+IND). Mean BP, which was not normalized with IND, was comparable for all groups. Systemic arterial compliance averaged 3.8, 2.5, 4.9, and 3.3 mL/mm Hg · 10 −3 , respectively, for the SHR, SHR+NaCl, SHR+IND, and SHR+NaCl+IND groups ( P <0.003 and <0.05 for NaCl and IND effects). Wall thickness increased only in the SHR+NaCl group ( P <0.01). Aortic wall COL decreased from 16 116 in the SHR to 12 382 μm 2 /mm in the SHR+NaCl+IND ( P <0.005) group. IND alone had no effect on elastin, but the elastin/collagen ratio was increased significantly. Aortic hyaluronan averaged 2343, 266, 3243, and 1052 μm 2 /mm, respectively, for the SHR, SHR+NaCl, SHR+IND, and SHR+NaCl+IND groups ( P <0.0001 for NaCl and IND effects). Changes in systemic arterial compliance were significantly and positively correlated with aortic hyaluronan contents. Thus, high-sodium diet affects the structural and functional characteristics of large arteries independently of BP. A high-sodium diet, in addition to a diuretic regimen with IND, affects simultaneously aortic hyaluronan contents and large artery mechanical properties through pressure-independent mechanisms that remain to be defined.