Demonstrating the immunohistochemical location of AT1R and AT2R in the stomach of the Mongolian gerbil. A-F shows sections from the antral region of an SS1-infected gerbil, 12 months after inoculation. A) Vascular smooth muscle cells (VSMC) in an artery located in the serosa stain positive for the AT1R protein (green color). B) Endothelial cells (end) and unidentified mesenchymal cells (m) located in the submucosa showing immunoreactivity for the AT2R protein. C) Smooth muscle cells in the muscular layer of the muscularis propria stain positive for the AT2R protein. D) A negative control (consecutive to the section in A) preabsorbed with the blocking peptide for the AT1R antibody, showing yellow autofluorescence from erythrocytes. E & F) Negative controls for the AT2R antibody, consecutive to the sections in B & C, respectively. G, H shows sections from the antral region of a control animal 6 months after inoculation and the section in (I) is from a TN2GF4-infected gerbil, 12 months after inoculation. Strong immunostaining for AT1R was found in cells with a typical appearance of endocrine cells (e). Muscularis mucosae (mm), muscularis propria (mp) and vascular smooth muscle cells (VSMC) also stained positive for the AT1R. A peroxidase based method (brown color) was used for staining of AT1R in G, H and immunofluorescence (green color) was used for staining of AT1R in (I). J, K and L) Consecutive sections from the antral region of a TN2GF4-infected gerbil, 6 months after inoculation. J) Immunostaining for AT1R (green color) shows aggregates of leucocytes (leu) expressing the AT1R protein. K) A negative control to the section in J, showing yellow autofluorescence from erythrocytes. L) The consecutive section to the section in K, routinely stained with H&E, confirming that the aggregates are leucocytes. M and N shows double immunostaining for AT1R (brown color in M) and for the pan-endocrine marker Chromogranin A (red color in N) of an antral section of a control animal. The white arrow in M and N points at a cell in the base of an antral gland that stained positive for both AT1R and Chromogranin A. Several of the Chromogranin A positive cells were not immunopositive to AT1R. Section O demonstrates neutrophils (PMNs) in the antral mucosa of an SS1-infected gerbil, 12 months after inoculation.