Abstract 201: In-Vivo Response of eNOS up-Regulation by Acoustic Induced Vibrations in Rats
Introduction: Pulsatile shear stress on the endothelium can induce up regulation of endothelial nitric oxide synthase (eNOS) and eNO release, and other vasoactive and cardioprotective products. These have been shown to decrease central and peripheral vascular resistances and have pre and post conditioning effects on ischemia reperfusion injury. Externally applied pulsations achieved with low frequency (200–800Hz) acoustic induced vibrations (AIV) might trigger similar up regulation processes. The aim of this study was to determine whether or not AIV induces eNO dependent vasodilatation and to study its frequency and power dependence
Methods: Male rats (±275 g) were instrumented for continuous monitoring of blood pressure, frequency of AIV and electrocardiogram. AIV was transferred to the skin of the sternum via a membrane. The effect of eNO induced vasodilatation due to AIV was studied at various frequencies and two powers (0.2W and 1.0W), by measuring descent of the dichrotic notch on the arterial pressure waveform (a/b ratio) and mean arterial blood pressure (MAP).To determine if the change in a/b ratio was due to eNOS up-regulation a dose response curve to an eNOS inhibitor (L-NAME) was performed.
Results: The rats tolerated AIV well, without increase in stress levels. Compared to control animals AIV induced a significant frequency and power dependent change in a/b. A significant change from baseline in a/b ratios occurred between 200 and 700Hz (p < 0.01), with a maximal increase in a/b of 70% at 300Hz and 1W (p < 0.01). MAP decreased at AIV exposure and showed similar optima as a/b ratio. Similar effects of lower magnitude were seen at the lower power of 0.2W. AIV blunted the initial increase in a/b (vasoconstriction) produced by L-NAME.
Conclusions: AIV produces peripheral vasodilatation as determined by an increase of a/b ratio and decrease of blood pressure. L-NAME blunted the a/b response to AIV. The latter suggest the effects to be due to eNO production via eNOS up-regulation. eNOS upregulation appears to be frequency dependent with optimum for AIV at 300Hz. AIV may be a valuable method to induce eNOS upregulation for therapeutic purposes.
- © 2010 by American Heart Association, Inc.