Cholecystokinin receptors in human pancreas and gallbladder muscle: A comparative study

Background & Aims: Cholecystokinin (CCK) receptors mediate pancreatic secretion and gallbladder contraction. Hitherto, little information on characteristics of CCK receptors in the human pancreas was available. This study identifies CCK receptors in the human pancreas and compares their characteristics with the CCK receptors in the human gallbladder. Methods: Visualization and quantification of I-125-Bolton-Hunter sulfated CCK octapeptide (I-125-BH-CCK-8) binding to tissue sections of the human pancreas and gallbladder were performed by storage phosphor autoradiography. Results: Specific bindings for CCK were visualized in pancreatic tissue and the smooth muscle layer of the gallbladder. Binding of I-125-BH-CCK-8 to the pancreas was inhibited by agonists with the affinities (dissociation constant) of CCK (0.11 nmol/L) approximate to gastrin (0.15 nmol/L) and by antagonists with the affinities of CCK-B receptor antagonist (L365,260, 0.18 nmol/L) > CCK-A receptor antagonist (lorglumide, 8.1 nmol/L). In contrast to the pancreas, binding of I-125-BH-CCK-8 to the gallbladder muscle was inhibited with high affinity by CCK-8 and lorglumide but was replaced to a small degree by gastrin and L365,260. Conclusions: The subtypes of receptors for CCK in the human pancreas and gallbladder are different. The human pancreas predominantly expresses CCK-B receptors, whereas only CCK-A receptors were localized in the human gallbladder muscle.