Radiographic evidence of cholecystokinin octapeptide receptors in the hamster gallbladder

Abstract

The distribution of cholecystokinin receptors in the hamster gallbladder was investigated by 125I-labeled Bolton-Hunter-cholecystokinin octapeptide autoradiography. Light microscopic examination showed a marked accumulation of radiolabeled cholecystokinin within the domain of the muscle layer of the gallbladder. The electron microscopic study further disclosed the presence of radiolabeling mostly in those areas corresponding to cell-to-cell junctions of smooth-muscle cells. Our results suggest that contraction of the gallbladder may primarily be induced by cholecystokinin interacting with its specific receptor in smooth-muscle cells. That cholecystokinin receptors were more abundant in the junctional complexes of smooth-muscle cells suggests that cholecystokinin may have a major role in muscle contraction of the gallbladder, which eventually produces an effective bile emptying.