title: Direct G protein activation reverses impaired CCK signaling in human gallbladders with cholesterol stones.
abstract: Human gallbladders were used to investigate the mechanisms of the impaired contraction induced by cholecystokinin (CCK) associated with cholesterol stones. Single muscle cells were isolated enzymatically with collagenase. Inositol 1,4,5-trisphosphate was measured by high-performance liquid chromatography. Diacylglycerol was assayed by thin-layer chromatography. CCK stimulation showed decreased muscle contraction and production of inositol 1,4,5-trisphosphate and diacylglycerol in gallbladders with cholesterol stones compared with those with pigment stones. Exogenous calmodulin induced maximal contraction of 22.4 +/- 0.5 and 21.0 +/- 0.6% in gallbladders with cholesterol and pigment stones, respectively. Similar findings were observed with a synthetic diacylglycerol analogue. Two G protein activators, aluminum fluoride and guanosine 5'-O-(3-thiotriphosphate), evoked similar responses in these two types of gallbladders, with maximal contractions of 21.3 +/- 0.4 and 23.3 +/- 0.5%, respectively, in those with cholesterol stones and 20.9 +/- 0.8 and 22.6 +/- 0.4%, respectively, in those with pigment stones. These results suggest that receptor-dependent ligands like CCK cannot fully activate the intracellular pathways, which, however, can be fully stimulated by circumventing receptors with G protein activators or second messengers. After G protein activation, the pathways appear to be functionally intact. The defect might then reside in the receptor or in the interaction between receptors and G proteins.
mesh_terms: D017607:Aluminum Compounds / Q000494:pharmacology; D002147:Calmodulin / Q000494:pharmacology; D002766:Cholecystokinin / Q000502:physiology*; D002769:Cholelithiasis / Q000473:pathology / Q000503:physiopathology*; D002784:Cholesterol / Q000378:metabolism*; D004075:Diglycerides / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005260:Female; D005459:Fluorides / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000502:physiology*; D005704:Gallbladder / Q000187:drug effects / Q000473:pathology / Q000503:physiopathology*; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D006801:Humans; D015544:Inositol 1,4,5-Trisphosphate / Q000096:biosynthesis; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction; D015398:Signal Transduction; D012844:Sincalide / Q000494:pharmacology
chemical_list: D017607:Aluminum Compounds; D002147:Calmodulin; D004075:Diglycerides; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D015544:Inositol 1,4,5-Trisphosphate; D002766:Cholecystokinin; D002784:Cholesterol; D019204:GTP-Binding Proteins; D012844:Sincalide; D005459:Fluorides; C032311:aluminum fluoride