LONG-TERM NITRIC-OXIDE SYNTHASE INHIBITION AND DISTENSIBILITY OF CAROTID-ARTERY IN INTACT RATS

The goal of the present study was to evaluate the effect of long-term nitric oxide synthase inhibition by N-G-nitro-L-arginine-methyl ester (L-NAME) on the morphology and viscoelastic properties of the carotid arteries in rats. Twelve-week-old Wistar-Kyoto rats were treated for 6 weeks with either the nitric oxide synthase inhibitor L-NAME (0.4 g/L in drinking water; L-NAME rats, n=13) or tap water (control rats, n=1 3). Age-matched spontaneously hypertensive rats (SHR, n=14) received t ap water for the same period. The internal diameter of the common caro tid artery was measured continuously with an echo-tracking device with the rats under anesthesia with halothane. Intra-arterial pressure was monitored an the contralateral side. L-NAME rats exhibited arterial p ressures similar to those of SHR. The distensibility pressure-curve de termined in L-NAME rats was a direct continuation of that obtained in control rats. in contrast the distensibility in SHR was increased (P<. 01, SHR versus L-NAME rats). Carotid artery cross-sectional area and l eft ventricular weight index were increased similarly in SHR and L-NAM E rats compared with control rats. Thus the hypertension caused by lon g-term nitric oxide synthesis inhibition was not associated with the i ncreased arterial distensibility observed in SHR despite similar blood pressure elevations, similar arterial hypertrophy, and consequently s imilar wall stress. This suggests a role for nitric oxide in regulatin g the mechanical behavior of arteries exposed to high blood pressure.