APStracts 2:0097G, 1995.

Direct g-protein activation reverses impaired cck-signaling in human gallbladders with cholesterol stones. Yu, Peirong, Qian Chen, Karen M. Harnett, Joseph Amaral, Piero Biancani, and Jose Behar. Departments of Medicine and Surgery, Rhode Island Hospital and Brown University School of Medicine, Providence, RI 02903

APStracts 2:0097G, 1995.

Human gallbladders were used to investigate the mechanisms of the impaired contraction induced by CCK associated with cholesterol stones. Single muscle cells were isolated enzymatically with collagenase. Inositol-1,4,5-trisphosphate was measured by HPLC. 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 to 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 analog. Two G-protein activators, aluminum fluoride and GTP[gamma]S, also 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. The pathways following G protein activation appear to be functionally intact. The defect might, then, reside in the receptor or in the interaction between receptors and G proteins.

Received 16 July 1994; accepted in final form 12 May 1995.
APS Manuscript Number G261-4.
Article publication pending Am. J. Physiol. (Gastrointest. Liver
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 26 May 1995.