Angiotensin II is a critical mediator of prazosin-induced angiogenesis in skeletal muscle

Abstract

Objective: The purpose of this study was to determine whether a high-salt diet modulates physiological angiogenesis in skeletal muscle by altering angiotensin II (ANGII) and vascular endothelial growth factor (VEGF) levels.

Methods: Sprague-Dawley rats were placed on a control diet (0.4% NaCl by weight) or high-salt diet (4.0% NaCl) prior to treatment with the vasodilator prazosin in the drinking water. In addition, a group of animals fed high salt were infused intravenously with ANGII at a low dose to prevent ANGII suppression by high salt, and a group of rats fed control diet were treated with the angiotensin II type I (AT(1)) receptor blocker losartan and prazosin.

Results: Prazosin induced significant angiogenesis in the tibialis anterior muscle after 1 week of treatment. High-salt-fed rats demonstrated a complete inhibition of this angiogenic response. Maintenance of ANGII levels restored prazosin-induced angiogenesis in animals fed a high-salt diet. In addition, losartan treatment blocked prazosin-induced angiogenesis in animals on a control diet. Western blot analysis indicated that prazosin-induced angiogenesis was independent of changes in muscle levels of VEGF.

Conclusions: This study demonstrates an inhibitory effect of high salt intake on prazosin-induced angiogenesis. Further, these results indicate that ANGII acting through the AT(1) receptor is a critical pathway in this model of angiogenesis.

Figure 1

Changes in TA muscle microvessel density following 1 or 2 weeks of prazosin treatment in rats on a control diet or a high-salt diet. * p < .05 vs. corresponding vehicle-treated rats. □, vehicle; , 1 wk Praz; ■, 2 wk Praz.

Figure 2

Changes in TA muscle microvessel density following 1 week of prazosin treatment in rats on a control diet, a high-salt diet, a high-salt diet and intravenous ANGII infusion, and a control diet with oral losartan treatment. * p < .05 vs. corresponding vehicle treated rats. □, vehicle; , 1 wk Praz.

Figure 3

A representative Western blot and results of quantitative densitometry of 6 separate Western blots comparing VEGF protein levels in the TA muscles of vehicle and prazosin-treated rats on a control diet, a high-salt diet, a high-salt diet with ANGII infusion, and a control diet with losartan treatment. □, vehicle; , 1 wk Praz.