sincalide and chelerythrine

Quercetin, a phytoestrogen and flavonoid, relaxes intestinal and vascular smooth muscle. The purpose of this study was to determine if quercetin had an effect on gallbladder smooth muscle. An in vitro technique was used to determine the effects of quercetin on gallbladder strips and which system(s) mediated the relaxation. Paired t tests were used; differences between means of P < .05 were considered significant. Adding quercetin before cholecystokinin or KCl produced a significant (P < .001) decrease in the amount of tension (0.80 ± 0.04 vs 0.48 ± 0.04 g cholecystokinin octapeptide and 0.8 ± 0.06 vs 0.54 ± 0.05 g KCl, respectively). When the protein kinase C (PKC) inhibitors bisindolymaleimide IV and chelerythrine Cl

Topics: Animals; Arginine; Benzophenanthridines; Boron Compounds; Calcium; Carbazoles; Cyclic AMP-Dependent Protein Kinases; Flavonoids; Gallbladder; Guinea Pigs; In Vitro Techniques; Indoles; Male; Maleimides; Muscle, Smooth; Nitric Oxide; Nitric Oxide Synthase; Potassium Chloride; Protein Kinase C; Protein Kinase Inhibitors; Quercetin; Signal Transduction; Sincalide

The role of protein kinase C (PKC) in sustained contraction was examined in intestinal circular and longitudinal muscle cells. Initial contraction induced by agonists (CCK-8 and neuromedin C) was abolished by 1) inhibitors of Ca(2+) mobilization (neomycin and dimethyleicosadienoic acid), 2) calmidazolium, and 3) myosin light chain (MLC) kinase (MLCK) inhibitor KT-5926. In contrast, sustained contraction was not affected by these inhibitors but was abolished by 1) the PKC inhibitors chelerythrine and calphostin C, 2) PKC-epsilon antibody, and 3) a pseudosubstrate PKC-epsilon inhibitor. GDPbetaS abolished both initial and sustained contraction, whereas a Galpha(q/11) antibody inhibited only initial contraction, implying that sustained contraction was dependent on activation of a distinct G protein. Sustained contraction induced by epidermal growth factor was inhibited by calphostin C, PKC-alpha,beta,gamma antibody, and a pseudosubstrate PKC-alpha inhibitor. Ca(2+) (0.4 microM) induced an initial contraction in permeabilized muscle cells that was blocked by calmodulin and MLCK inhibitors and a sustained contraction that was blocked by calphostin C and a PKC-alpha,beta,gamma antibody. Thus initial contraction induced by Ca(2+), agonists, and growth factors is mediated by MLCK, whereas sustained contraction is mediated by specific Ca(2+)-dependent and -independent PKC isozymes. G protein-coupled receptors are linked to PKC activation via distinct G proteins.

Topics: Alkaloids; Animals; Antibodies; Benzophenanthridines; Bombesin; Calcium; Carbazoles; Enzyme Inhibitors; Epidermal Growth Factor; Fatty Acids, Unsaturated; Guinea Pigs; Imidazoles; In Vitro Techniques; Indoles; Intestines; Isoenzymes; Muscle Contraction; Muscle, Smooth; Myosin-Light-Chain Kinase; Naphthalenes; Neomycin; Peptide Fragments; Phenanthridines; Phosphodiesterase Inhibitors; Protein Kinase C; Protein Kinase C beta; Protein Kinase C-alpha; Protein Kinase C-epsilon; Protein Synthesis Inhibitors; Sincalide

Receptor-mediated activation of phosphatidylcholine phosphatidohydrolase or phospholipase D (PLD) was studied in Chinese hamster ovary (CHO) cells expressing the cholecystokinin-A (CCK-A) receptor. Cells were labelled with [3H]myristic acid for 24 h and PLD-catalysed [3H]phosphatidylethanol formation was measured in the presence of 1% (v/v) ethanol. Cholecystokinin-(26-33)-peptide amide (CCK8) increased PLD activity both time- and dose-dependently. Maximal activation of protein kinase C (PKC) with 1 microM PMA or sustained elevation of the cytosolic free Ca2+ concentration ([Ca2+]i) with 1 microM thapsigargin increased PLD activity to 50% and 70% of the maximal value obtained with CCK8 respectively. The stimulatory effects of CCK8, PMA and thapsigargin were abolished in cells in which PKC was downregulated or inhibited by chelerythrine. PMA/Ca2+-stimulated PLD activity was absent in a homogenate of PKC-downregulated cells but could be restored upon addition of purified rat brain PKC. CCK8-induced PLD activation was inhibited by 90% in the absence of external Ca2+, demonstrating that receptor-mediated activation of PKC in itself does not significantly add to PLD activation but requires a sustained increase in [Ca2+]i. Taken together, the results presented demonstrate that, in CHO-CCK-A cells, receptor-mediated PLD activation is completely dependent on PKC, but that the extent to which PLD becomes activated depends largely, if not entirely, on the magnitude and duration of the agonist-induced increase in [Ca2+]i.

Topics: Alkaloids; Animals; Benzophenanthridines; Brain; Calcium; CHO Cells; Cricetinae; Cytosol; Down-Regulation; Enzyme Activation; Glycerophospholipids; Phenanthridines; Phospholipase D; Protein Kinase C; Protein Kinase Inhibitors; Rats; Receptor, Cholecystokinin A; Receptors, Cholecystokinin; Recombinant Proteins; Sincalide; Tetradecanoylphorbol Acetate; Thapsigargin

Smooth muscle from gallbladders with cholesterol stones exhibits impaired response to cholecystokinin (CCK). This study investigated whether the impaired response is mediated by different signal-transduction pathways responsible for CCK-induced contraction in prairie dog and human gallbladders with cholesterol stones. Gallbladder muscle cells were isolated enzymatically to study contraction. Protein kinase C (PKC) activity was measured by examining the phosphorylation of a specific substrate peptide from myelin basic protein Ac-MBP-(4-14). Gallbladder muscle cells from high-cholesterol-fed prairie dogs contracted less in response to CCK octapeptide (CCK-8) than those from the control group. However, inositol-1,4,5-trisphosphate (IP3), diacylglycerol, and guanosine 5'-O-(3-thiotriphosphate) induced the same magnitudes of contraction in these two groups. In control prairie dog and human gallbladders, the maximal contraction caused by 10(-8) M CCK-8 was blocked by the calmodulin antagonist CGS9343B but not by the PKC inhibitor H-7. Conversely, in gallbladders with cholesterol stones from prairie dogs or human patients, the maximal contraction induced by 10(-8) M CCK-8 was blocked by H-7 and chelerythrine but not by CGS9343B. In these gallbladders CCK-8 caused a significant PKC translocation from the cytosol to the membrane. High CCK concentrations may activate the calmodulin-dependent pathway in functionally normal gallbladder muscle and the PKC-dependent pathway in muscle from gallbladders with cholesterol stones. The defect of gallbladder muscle after cholesterol feeding and stones might reside in the steps before G protein activation.

Topics: 1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; Alkaloids; Animals; Benzimidazoles; Benzophenanthridines; Biological Transport; Calmodulin; Cholecystokinin; Cholelithiasis; Enzyme Inhibitors; Gallbladder; Humans; Male; Muscle Contraction; Muscle, Smooth; Phenanthridines; Protein Kinase C; Reference Values; Sciuridae; Sincalide