Arteriolar network morphology in gracilis muscle of rats with salt-induced hypertension

The purpose of this study was to determine if structural rarefaction of arterioles occurs in the gracilis muscle of Dahl salt-sensitive (DS) rats with salt-induced hypertension. Arteriolar network architecture was studied in cleared muscles removed from DS fed either a high (7% NaCl) or low-normal (0.45% NaCl) salt diet for 4 weeks. Muscles removed from Dahl salt-resistant (DR) rats on high and low-normal salt diets served as controls. The 7% NaCl diet had no effect on arterial pressure in DR, but caused marked hypertension in DS. The density of arcade arterioles was significantly lower in DS than in DR (0.77 vs 1.26 segments/mg tissue, respectively) and was unrelated to either dietary salt content or mean arterial pressure in both strains. The number of transverse arterioles/mm parent vessel was 19% lower in DS on 7% NaCl than in DS on 0.45% NaCl and DR on either diet. These data indicate that compared to normotensive DR, the DS rat with salt-induced hypertension exhibits a lower vascular density within both the arcading and the transverse portions of the gracilis muscle arteriolar network. The lower arcade vessel density reflects an inherent characteristic of the DS strain, whereas the lower transverse arteriole density reflects a true structural rarefaction associated with salt-induced hypertension.