Proceedings of the High Blood Pressure Research Council of Australia - Basilar artery remodelling in the genetically hypertensive rat: Effects of nitric oxide synthase inhibition and treatment with valsartan and enalapril

1. The structure of the basilar artery and the relationship of structure to blood pressure and ventricular hypertrophy was examined in genetically hypertensive (GH) rats, their control normotensive (N) Wistar strain, GH given the nitric oxide synthase (NOS) inhibitor, N-G-nitro-L-arginine methyl ester (L-NAME) and GH given L-NAME and either valsartan or enalapril. 2. Systolic blood pressure (SBP; tail-cuff) was measured weekly from age 7-12 weeks. At the end of the experiment at 12 weeks, the basilar artery was fixed by perfusion and embedded in Technovit (Heraeus Kulzer GmbH, Werheim, Germany). Serial sections were cut and stained and stereological analysis applied to quantify the morphology of the vessels. Left ventricular (LV) mass was determined. 3. Both SBP and LV mass were significantly increased in GH compared with N (P < 0.001) and increased further in GH given L-NAME (P < 0.05). The GH L-NAME + valsartan and GH L-NAME + enalapril groups had significantly lower (P < 0.001) SBP and LV mass than the GH L-NAME group. 4. Basilar arteries in GH (which are frankly hypertensive, but have no apparent endothelial defect) showed hypotrophic inward remodelling compared with the N control group with no change in media to lumen ratio. 5. In the GH L-NAME group, further inward remodelling occurred and the media to lumen ratio was increased compared with N (P < 0.01) and GH (P < 0.05). Valsartan treatment in GH L-NAME rats caused eutrophic outward remodelling. Enalapril caused hypertrophic outward remodelling, suggesting that the angiotensin II-stimulated growth was not entirely suppressed with an angiotensin-converting enzyme inhibitor or that there was a bradykinin effect with enalapril. 6. In GH with an endothelial defect induced by treatment with L-NAME, the further remodelling, together with an increased media to lumen ratio and the development of a stroke-like syndrome, indicates the NOS-inhibited GH rat may be a useful model for essential hypertension (where it is known that endothelial abnormalities exist) and where stroke can develop as a consequence of the hypertension.