Comparative effects of the angiotensin II receptor blocker, telmisartan, and the angiotensin-converting enzyme inhibitor, ramipril, on cerebrovascular structure in spontaneously hypertensive rats

Objective Antihypertensive treatment with angiotensin-converting enzyme inhibitors (ACEIs) reverses cerebral arteriolar remodeling, thus restoring dilatation and hence the lower limit of cerebral blood flow (CBF) autoregulation (LLCBF). The objective of this study was to determine whether angiotensin II receptor AT(1) blockers (ARBs) produce the same effect. Design We examined the effects of treatment with an ARB [telmisartan (TEL), 1.93 +/- 0.04 mg/kg per day] or an ACEI [ramipril (RAM), 1.00 +/- 0.02 mg/kg per day] on the cerebral circulation in spontaneously hypertensive rats (SHR). Methods Arteriolar pressure and diameter (cranial window) and CBF (laser Doppler) were measured during stepwise hypotensive hemorrhage, before and after deactivation (ethylenediamine tetraacetic acid), in untreated Wistar-Kyoto (WKY) rats and SHR untreated or treated for 3 months with TEL or RAM in the drinking water. Results Treatment normalized arteriolar internal diameter (SHR, 38 +/- 3 mu m; TEL, 52 +/- 2 mu m; RAM, 50 +/- 2 mu m; WKY, 58 +/- 4 mu m), essentially by reversing eutrophic inward remodeling, and the LLCBF (SHR, 80 +/- 11 mmHg; TEL, 60 +/- 4 mmRAM, 71 +/- 6 mmHg; WKY, 57 +/- 5 mmHg). Conclusion The fact that the ARB (TEL) is as effective as an ACEI (RAM) in reversing cerebral arteriolar remodeling suggests that the cerebrovascular AT, receptor is an underlying mechanism that promotes hypertensive eutrophic inward remodeling. (c) 2005 Lippincott Williams & Wilkins.