CHRONIC NITRIC-OXIDE SYNTHASE INHIBITION AND CAROTID-ARTERY DISTENSIBILITY IN RENAL HYPERTENSIVE RATS

The goal of the present study was to examine the viscoelastic properties of the carotid artery in genetically identical rats exposed to similar levels of blood pressure sustained by different mechanisms. Eight-week-old male Wistar rats were examined 2 weeks after renal artery clipping (two-kidney, one clip [2K1C] Goldblatt rats, n=53) or sham operation (n=49). One half of the 2K1C and sham rats received the nitric oxide synthase inhibitor N-G-nitro-L-arginine methyl ester (L-NAME, 1.48 mmol/L) in their drinking water for 2 weeks after the surgical procedure. Mean blood pressure increased significantly in the 2K1C-water (182 mm Hg), 2K1C-L-NAME (197 mm Hg), and sham-L-NAME (170 mm Hg) rats compared with the sham-water rats (127 mm Hg). Plasma renin activity was not altered by L-NAME but significantly enhanced after renal artery clipping. A significant and similar increase in the cross-sectional area of the carotid artery was observed in L-NAME- and vehicle-treated 2K1C rats. L-NAME per se did not modify cross-sectional area in the sham rats. There was a significant upward shift of the distensibility-pressure curve in the L-NAME- and vehicle-treated 2K1C rats compared with the sham-L-NAME rats. L-NAME treatment did not alter the distensibility-pressure curve in the 2K1C rats. These results demonstrate that the mechanisms responsible for artery wall hypertrophy in renovascular hypertension are accompanied by an increase in arterial distensibility that is not dependent on the synthesis of nitric oxide.