Distribution of endothelin-B receptor-like immunoreactivity in rat brain, kidney, and pancreas

We investigated the distribution of endothelin B (ETB) receptor-like immunoreactivity in rat brain, kidney, and pancreas, using an antiserum against amino acid residues 425-439 of the rat ETB receptor modified by the multiple-antigen peptide complex system. In the brain, immunoreactive fibers were observed mainly in the hypothalamus and diagonal band of Broca. Densely arranged immunoreactive fibers were observed in the organum vasculosum of the lamina terminalis and the median eminence. In these areas, the immunoreactive fibers corresponded to luteinizing hormone-releasing hormone-immunoreactive fibers. In the kidney, intense ETB receptor-like immunoreactivity was seen in structures that were presumably proximal tubules. In other segments of renal tubules and collecting ducts, immunoreactive puncta were scattered. In the glomerulus, a few immunoreactive puncta were seen on the capillaries. In the pancreas, ETB receptor-like immunoreactivity was seen in the acinar cells and islets of Langerhans. By analysis of double staining in the same section, B and D cells showed intense immunoreactivity, whereas A cells showed only weak immunoreactivity. These results suggest that the ETB receptor or its subtype is localized in specific cell types in the organs investigated. In these cells, ET(s) may modulate the function of each cell type via this type of receptor.