Surgery · 1993
Characterization of cholecystokinin receptors on the human sphincter of Oddi.
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Tokunaga Y, Cox K L, Itasaka H, Concepcion W, Nakazato P, Esquivel C O
Аннотация
BACKGROUND: The present in vitro study investigated the interaction between cholecystokinin (CCK) and receptors on human sphincter of Oddi tissue obtained from donated human livers that were being transplanted.
METHODS: Radiolabeled ligands with cholecystokinin receptor specificity, autoradiography, and crystal scintillation counting were used to directly characterize cholecystokinin receptors on tissue sections.
RESULTS: The binding of 125I-BH-CCK-8 to the tissue was saturable, specific, and dependent on time, pH, and temperature. Saturable binding of 125I-BH-CCK-8 was localized on the smooth muscle layer, and binding was inhibited only by cholecystokinin-related peptides. Computer analysis of 125I-BH-CCK-8 binding indicated the presence of two classes of binding sites, one with a high affinity and the other with a low affinity for CCK-8. CCK-8 caused relaxation (half-maximal concentration, 6 nmol/L) and carbachol caused contraction (half-maximal concentration, 10 nmol/L) of circular, cross-sectional strips of the tissue. Longitudinal strips were less responsive. The relative 125I-BH-CCK-8 binding inhibition potency of CCK-8 agreed closely with its relative ability to cause sphincter relaxation. Tetrodotoxin (1 mumol/L) and atropine (1 mumol/L) caused a rightward shift of the dose-response curve for CCK-8-stimulated sphincter relaxation.
CONCLUSIONS: The present results indicate that cholecystokinin receptors on the human sphincter of Oddi are sulfate dependent and mediate sphincter relaxation.
METHODS: Radiolabeled ligands with cholecystokinin receptor specificity, autoradiography, and crystal scintillation counting were used to directly characterize cholecystokinin receptors on tissue sections.
RESULTS: The binding of 125I-BH-CCK-8 to the tissue was saturable, specific, and dependent on time, pH, and temperature. Saturable binding of 125I-BH-CCK-8 was localized on the smooth muscle layer, and binding was inhibited only by cholecystokinin-related peptides. Computer analysis of 125I-BH-CCK-8 binding indicated the presence of two classes of binding sites, one with a high affinity and the other with a low affinity for CCK-8. CCK-8 caused relaxation (half-maximal concentration, 6 nmol/L) and carbachol caused contraction (half-maximal concentration, 10 nmol/L) of circular, cross-sectional strips of the tissue. Longitudinal strips were less responsive. The relative 125I-BH-CCK-8 binding inhibition potency of CCK-8 agreed closely with its relative ability to cause sphincter relaxation. Tetrodotoxin (1 mumol/L) and atropine (1 mumol/L) caused a rightward shift of the dose-response curve for CCK-8-stimulated sphincter relaxation.
CONCLUSIONS: The present results indicate that cholecystokinin receptors on the human sphincter of Oddi are sulfate dependent and mediate sphincter relaxation.