Modifications of the Arterial Mechanical Properties of Normotensive and Hypertensive Rats Without Arterial Pressure Changes

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Abstract
Possible reduction in arterial thickness may be an interesting way to reduce left ventricular afterload in various pathologic conditions. We tested the effects of cicletanine (3 mg/kg) on the systemic hemodynamics and the mechanical properties of the arterial walls in 12-week-old normotensive Wistar Kyoto (WkY) rats and spontaneously hypertensive rats (SHR). The mechanical properties of the arterial walls were assessed using three independent methods: the characteristic impedance of the ascending aorta (Zc), systemic arterial compliance (SAC), and compliance of the carotid artery (CC). Zc and SAC were calculated from phasic records of pressure and flow in the ascending aorta; CC was measured in situ with or without smooth muscle cell activity [potassium cyanide (KCN) poisoning]. After chronic therapy by daily gavage for 15 days, there were no significant changes in either WKY and SRH in terms of arterial blood pressure (BP), cardiac output (CO), and heart rate (HR). In contrast, Zc, SAC, and passive distensibility of the isolated carotid arteries were significantly improved in treated groups. The increase in arterial distensibility reflected modifications in function (smooth muscle tone) of the arterial wall after cicletanine chronic therapy. Although the exact mechanisms of the observed changes in arterial mechanics remain unclear, this study showed that in experimental hypertension cicletanine can affect distensibility of large arteries independent of significant changes in BP.

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