The present study reports an immunohistochemical approach for localizing the immunoreactivity of
vasoactive intestinal polypeptide (
VIP) receptor in the human colon, by using a
monoclonal antibody which recognizes the
VIP-receptor of a human colonic
adenocarcinoma cell line. Simultaneous demonstration of immunoreactive
VIP-receptor of a human colonic
adenocarcinoma cell line. Simultaneous demonstration of immunoreactive
VIP-receptor and VIP was achieved by a double-labelling procedure employing immunogold
silver staining for
VIP-receptor, and a biotinylated secondary antibody followed by
streptavidin-
Texas Red, to visualize VIP. The immunoreactive
VIP receptor was found at two locations receiving dense VIP innervation: myenteric ganglia and mucosal epithelium. Epithelial cells displayed intense labelling at the basolateral membrane, which confirmed earlier binding studies on fractionated membranes. A small number of enteroendocrine cells was also recognized by the
VIP-receptor antibody. Smooth muscle and cells of the immune system were not stained by the
monoclonal antibody, indicating that it recognized an
epitope not common to
VIP-receptors of all locations. Thus, the immunohistochemical approach of
VIP-receptor localization differs from autoradiography in (a) precise cellular localization, (b) possibility of simultaneous demonstration of receptor and
ligand immunoreactivity, and (c) selectivity to a certain receptor population which, however, is presently not fully characterized.