Mas receptors in modulating relaxation induced by perivascular adipose tissue

Aims: Perivascular adipose tissue (PVAT) is known to secrete vascular relaxation factors, and angiotensin 1-7 [Ang-(1-7)] acting on the endothelium is one of the endothelium-dependent relaxation factors. Mas protein is the receptor for Ang-(1-7). Using aorta from Mas-knockout (K/O) and wild type (FVB) mice, we wished to establish the essential role of Mas receptors in mediating the endothelium-dependent relaxation response induced by relaxation factors from PVAT. Main methods: Thoracic aortic rings from K/O and FVB mice were prepared with or without PVAT (PVAT+ and PVAT-) and/or intact endothelium (E+) or with the endothelium removed (E-) for functional studies. The contraction and relaxation responses of these vessels to agonist in the presence of different receptor antagonists were studied. Key findings: PVAT attenuated the contraction induced by phenylephrine (PHE) in the presence of endothelium only in vessels from FVB mice. Mas receptor antagonists D-Ala-Ang-(1-7) (A779) or D-Pro(7)-Ang-(1-7) enhanced the contraction induced by PHE only in vessels from FVB mice. Ang-(1-7) caused a relaxation response only in E+ vessels from FVB mice. Transfer of donor solution from PVAT+ vessels to PVAT- recipient vessels caused a relaxation response among FVB vessels and not among vessels from K/O mice. Significance: Mas receptors are essential in mediating the endothelium-dependent relaxation response induced by PVAT, therefore highlighting the important role of Ang-(1-7) in the control of vascular functions through PVAT. (C) 2011 Elsevier Inc. All rights reserved.