Constriction of resistance arteries determines l-NAME-induced hypertension in a conscious hamster model

The influence of infusion of a nitric oxide (NO) synthase inhibitor, N(omega)-nitro-l-arginine methyl ester (l-NAME), on resistance arteries (diameter, 150 +/- 8 microm) and its relationship with hypertension were examined in conscious hamsters fitted with a dorsal skinfold window. After infusing l-NAME (10 and 30 mg/kg), hamsters showed immediate hypertension of +13 +/- 9 and +21 +/- 9 mm Hg, respectively, relative to basal values, and a maximum of +44 +/- 4 mm Hg at 30 min for the high-dose group. There was simultaneous significant vasoconstriction of the resistance arteries (A(0)) which reduced to 60 +/- 5% of baseline diameter at 3 h; however, there was no significant vasoconstriction in large and small arterioles with diameters diameters less than 70 microm. Blood flow rate in all the vessels decreased in consonance with the vasoconstriction of the resistance artery, irrespective of microvessel classification. These results indicate that the resistance artery plays a key role as a regulator and microvascular resistance in determining blood flow distribution and hypertension when a NO synthase inhibitor is infused.