Localization of the ANG II type 2 receptor in the microcirculation of skeletal muscle

1 Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin 53226; and 2 Department of Biological Sciences and Institute for Biochemistry and Biotechnology, Oakland University, Rochester, Michigan 48309 Only functional studies have suggested the presence of the ANG II type 2 (AT 2 ) receptor in the microcirculation. To determine the distribution of this receptor in the rat skeletal muscle microcirculation, a polyclonal rabbit anti-rat antiserum was developed and used for immunohistochemistry and Western blot analysis. The antiserum was prepared against a highly specific and antigenic AT 2 -receptor synthetic peptide and was validated by competition and sensitivity assays. Western blot analysis demonstrated a prominent, single band at ~40 kDa in cremaster and soleus muscle. Immunohistochemical analysis revealed a wide distribution of AT 2 receptors throughout the skeletal muscle microcirculation in large and small microvessels. Microanatomic studies displayed an endothelial localization of the AT 2 receptor, whereas dual labeling with smooth muscle -actin also showed colocalization of the AT 2 receptor with vascular smooth muscle cells. Other cells associated with the microvessels also stained positive for AT 2 receptors. Briefly, this study confirms previous functional data and localizes the AT 2 receptor to the microcirculation. These studies demonstrate that the AT 2 receptor is present on a variety of vascular cell types and that it is situated in a fashion that would allow it to directly oppose ANG II type 1 receptor actions. immunohistochemistry; vascular smooth muscle cell; endothelial cell; microvessels; angiotensin II