Altered structure and reduced distensibility of arteries in Dahl salt-sensitive rats

OBJECTIVES: The role of salt sensitivity in arterial stiffening and the structural basis of reduced arterial distensibility were investigated in Dahl salt-sensitive (DS) rats. METHODS: Three-month-old male DS rats received a normal (0.7% NaCl) or a high-sodium (2% NaCl) diet for 3 months. Dahl salt-resistant (DR) rats were controls. Pressure-volume (distensibility) relationships were measured in in-vitro-perfused segments of right carotid and iliac arteries, in the presence and absence of extracellular calcium. The left carotid and iliac arteries were perfusion-fixed at 100 mmHg for morphometric measurements. RESULTS: The average monthly tail systolic blood pressure (SBP) of DS rats on normal and high-sodium diets were increased compared to that of DR rats. Compared to controls, carotid and iliac artery pressure-volume curves of DS rats on normal and high-sodium diets were shifted toward the pressure axis, without a change in elastic moduli. In DS rats, reduced distensibility of the carotid artery was accompanied by increased lumen diameter and increased thickness of media and elastic lamellae, the wall to lumen ratio being unchanged; wall thickness was increased and lumen diameter unchanged in the iliac artery. The high-sodium diet had no effect on either distensibility or dimensions of carotid and iliac arteries in DS or DR rats. CONCLUSION: Geometry (increased or unchanged lumen and increased wall thickness), rather than increased stiffness of wall components, appears to be the cause of reduced distensibility of arteries in DS rats. Structural and functional adaptation to salt sensitivity may occur on what is considered a 'normal' sodium diet.