Blunted increases in vertebral blood flow during L‐arginine infusion in patients with hypertension (1183.5)

Abstract

Arterial hypertension (AH) has detrimental effects on the physiological mechanisms that regulate blood supply to the brain. However, little is known about the impact of human AH on cerebral endothelial function. In 21 men, 13 hypertensive patients (46±3 yr) and 8 age‐matched controls (Ctrl; 44±4 yr), blood pressure (Finometer) and blood flow (Doppler) in the main arteries delivering blood to the cortex (common carotid, CC) and brainstem (vertebral, VA) were simultaneously measured at rest and during 30 min of intravenous infusion of L‐arginine (30g) or saline. We systematically administered L‐arginine, a precursor of nitric oxide, to examine the nitric oxide‐mediated regional cerebral vasomotor regulation. Compared to controls, patients with AH had similar resting CC (AH: 601±30 vs. Ctrl: 571±43 mL/min) and VA blood flow (AH: 109±11 vs. Ctrl: 105±11 mL/min). On administration of L‐arginine, the CC blood flow was similarly increased in both groups (AH: +11±4% vs. Ctrl: +13±3% at 25‐30 min). In contrast, increases in VA blood flow were blunted in AH patients (AH: +1±3% vs. Ctrl: +16±4% at 25‐30 min; P<0.05). BP decreased by ‐5±3% (P<0.05) in both groups during L‐arginine infusion. All variables returned near resting values after infusion. Blood flow and BP were unchanged during saline infusion. Our results indicate a diminished endothelial function within the brainstem circulation of patients with hypertension.Grant Funding Source: Supported by CAPES, CNPq, FAPERJ.