Immunocytochemical identification of low-affinity NTS2 neurotensin receptors in parietal cells of human gastric mucosa

Abstract

The biological effects of neurotensin (NT) are mediated by two distinct G protein-coupled receptors, NTS1, and NTS2. Although it is well established that neuratensin inhibits gastric acid secretion in man, the plasma membrane receptor mediating these effects has not been visualized yet. We developed and characterized a novel antipeptide antibody to the carboxy-terminal region of the human NTS2 receptor. The cellular and subcellular distribution of NTS2 receptors was evaluated in various human gastrointestinal tissues. Specificity of the antiserum was demonstrated by (1) detection of a broadband migrating at Mr, 90 000-100 000 in Western blots of membranes from NTS2-expressing tissues; (2) cell-surface staining of NTS2-transfected cells; (3) translocation of NTS2 receptor immunostaining after agonist exposure; and (4) abolition of tissue immunostaining by preadsorbtion of the antibody with its immunizing peptide. In the gastrointestinal tract, NTS2 receptor immunoreactivity was highly abundant in parietal cells of the gastric mucosa, in neuroendocrine cells of the stomach small and large intestine, and in cells of the exocrine pancreas. NTS2 receptors were clearly located in the plasma membrane and uniformly present on nearly all target cells. The presence of NTS2 receptors was rarely detected in human tumors. This is the first localization of NTS2 receptors in human formalin-fixed, paraffin-embedded tissues at the cellular level. The abundant expression of low-affinity NTS2 receptors on the plasma membrane of human parietal cells provides a morphological substrate for the direct inhibition of gastric acid secretion observed after i.v. administration of neurotensin. © 2006 Society for Endocrinology.