NO EVIDENCE FOR VASCULAR REMODELING DURING HYPERTENSION INDUCED BY CHRONIC INHIBITION OF NITRIC-OXIDE SYNTHASE IN BRATTLEBORO RATS

Objective: To examine the effects of hypertension induced by chronic inhibition of nitric oxide synthase with N-G-nitro-L-arginine methyl ester (L-NAME) on the structure of mesenteric resistance arteries. Design and methods: Brattleboro rats were given L-NAME (0.01-0.05 mg/ml, equivalent to 10-50 mg/kg per day) in their drinking water for 2-3 weeks. On the day of the experiment, mean arterial pressure was measured directly using an intra-arterial catheter that had been implanted 2 days previously. Isolated mesenteric resistance arteries were set up in a pressure-perfusion myograph in a calcium-free physiological solution and subsequently fixed with glutaraldehyde, embedded in Araldite sectioned and examined histologically. Results: L-NAME administration increased mean arterial blood pressure in comparison with normotensive controls. No differences were found between the structural characteristics of mesenteric resistance arteries of first (pressurized diameter approximately 350 mu m), second (approximately 270 mu m) or third (approximately 200 mu m) order vessels isolated from normotensive rats and rats that had been treated with L-NAME. There were no significant correlations between mean arterial blood pressure and the variables of internal diameter, media thickness and media:lumen area ratio. Conclusions: Hypertension produced by chronic inhibition of nitric oxide synthase is not associated with remodelling of mesenteric resistance arteries in Brattleboro rats.