Human Gallbladder Muscle Research Articles

Mechanism of resveratrol-induced relaxation in the human gallbladder

BackgroundResveratrol is a polyphenolic compound extracted from plants and is also a constituent of red wine. Resveratrol produces relaxation of vascular smooth muscle and may prevent cardiovascular diseases. Although resveratrol has been reported to cause relaxation of the guinea pig gallbladder, limited data are available about the effect of resveratrol on the gallbladder smooth muscle in humans. The purpose of this study was to investigate the relaxation effects of resveratrol in human gallbladder muscle strips.MethodsWe studied the relaxant effects of resveratrol in human gallbladder. In addition, we also investigated mechanism of resveratrol-induced relaxation in human gallbladder by tetraethylammonium (a non-selective potassium channels blocker), iberiotoxin (an inhibitor of large conductance calcium-activated potassium channel), glibenclamide (an ATP-sensitive potassium channel blocker), charybdotoxin (an inhibitor of large conductance calcium-activated potassium channels and slowly inactivating voltage-gated potassium channels), apamine (a selective inhibitor of the small conductance calcium-activated potassium channel), KT 5720 (a cAMP-dependent protein kinase A inhibitor), KT 5823 (a cGMP-dependent protein kinase G inhibitor), NG-Nitro-L-arginine (a competitive inhibitor of nitric oxide synthase), tetrodotoxin (a selective neuronal Na+ channel blocker), and ω-conotoxin GVIA (a selective neuronal Ca2+ channel blocker).ResultsThe present study showed that resveratrol has relaxant effects in human gallbladder muscle strips. In addition, we found that resveratrol-induced relaxation in human gallbladder is associated with nitric oxide, ATP-sensitive potassium channel, and large conductance calcium-activated potassium channel pathways.ConclusionsThis study provides the first evidence concerning the relaxant effects of resveratrol in human gallbladder muscle strips. Furthermore, these results demonstrate that resveratrol is a potential new drug or health supplement in the treatment of biliary colic.

Muscarinic receptor M3 mediates human gallbladder contraction through voltage-gated Ca2+ channels and Rho kinase

Objective. Muscarinic receptors mediate contraction of the human gallbladder through unclear receptor subtypes. The aim of the present study was to characterize muscarinic acetylcholine receptors mediating contraction of the human gallbladder. Materials and methods. Contraction of human gallbladder muscle strips caused by agonists carbachol and muscarine was measured and the inhibition of carbachol-induced contraction by muscarinic receptor antagonists was evaluated. Reverse transcription polymerase chain reaction was performed to determine the existence of muscarinic receptor subtypes. Results. Carbachol and muscarine caused concentration-dependent contraction of gallbladder strips. Four receptor antagonists, including atropine, 4-diphenylacetoxy-N-methylpiperidine methiodide (4-DAMP), methoctramine, and pirenzepine, inhibited the carbachol-induced contraction. The relative inhibitory potency of these receptor antagonists was atropine > 4-DAMP > methoctramine > pirenzepine. The antagonist affinity estimates (pA2 values) correlated with the known affinities at M3, M4, and M5 muscarinic receptors. In addition, the M4-selective antagonist muscarinic toxin 3 did not inhibit and the M5-selective positive allosteric modulator VU0238429 did not potentiate carbachol-induced gallbladder contraction. This suggests that M3 muscarinic receptors mediate the muscarinic response predominantly. The contractile response of carbachol was attenuated by the voltage-gated Ca2+ channel inhibitor nifedipine and Rho-kinase inhibitor H-1152, but not affected by protein kinase C inhibitor chelerythrine. This implies the involvement of voltage-gated Ca2+ channel and Rho kinase but not protein kinase C. Conclusions. These results suggest a major role of M3 muscarinic receptors mediating the human gallbladder contraction through voltage-gated Ca2+ channels and Rho kinase. M3-selective muscarinic receptor antagonists could be of therapeutic importance in the treatment of biliary motility disorders.

Effects of cholesterol on CCK-1 receptors and caveolin-3 proteins recycling in human gallbladder muscle

The contraction of gallbladders (GBs) with cholesterol stones is impaired due to high cholesterol concentrations in caveolae compared with GBs with pigment stones. The reduced contraction is caused by a lower cholecystokinin (CCK)-8 binding to CCK-1 receptors (CCK-1R) due to caveolar sequestration of receptors. We aimed to examine the mechanism of cholesterol-induced sequestration of receptors. Muscle cells from human and guinea pig GBs were studied. Antibodies were used to examine CCK-1R, antigens of early and recycling endosomes, and total (CAV-3) and phosphorylated caveolar-3 protein (pCAV-3) by Western blots. Contraction was measured in muscle cells transfected with CAV3 mRNA or clathrin heavy-chain small-interfering RNA (siRNA). CCK-1R returned back to the bulk plasma membrane (PM) 30 min after CCK-8 recycled by endosomes, peaking at 5 min in early endosomes and at 20 min in recycling endosomes. Pretreatment with cholesterol-rich liposomes inhibited the transfer of CCK-1R and of CAV-3 in the endosomes by blocking CAV-3 phosphorylation. 4-Amino-5-(4-chloro-phenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine (inhibitor of tyrosine kinase) reproduced these effects by blocking pCAV-3 formation, increasing CAV-3 and CCK-1R sequestration in the caveolae and impairing CCK-8-induced contraction. CAV-3 siRNA reduced CAV-3 protein expression, decreased CCK-8-induced contraction, and accumulated CCK-1R in the caveolae. Abnormal concentrations of caveolar cholesterol had no effect on met-enkephalin that stimulates a delta-opioid receptor that internalizes through clathrin. We found that impaired muscle contraction in GBs with cholesterol stones is due to high caveolar levels of cholesterol that inhibits pCAV-3 generation. Caveolar cholesterol increases the caveolar sequestration of CAV-3 and CCK-1R caused by their reduced recycling to the PM.

High levels of caveolar cholesterol inhibit progesterone-induced genomic actions in human and guinea pig gallbladder muscle.

Gallbladder disease is prevalent during pregnancy. It has been suggested that this complication of pregnancy is attributable to increased bile cholesterol (Ch) induced by estrogens and to gallbladder hypomotility caused by increasing levels of progesterone (P4). Studies on nonpregnant gallbladders have shown that increased levels of bile Ch contribute to both gallstone formation and bile stasis. These studies investigated the effects of high levels of plasma membrane Ch on P4 on gallbladder muscle cells from human and guinea pigs. Contraction was studied in intact and permeabilized muscle cells. G proteins were determined by Western blot, and 3H-P4 incorporation by muscle cells was measured in the beta-scintillation counter. High levels of caveolar Ch blocked the effects induced by P4 treatment for 6 h. They suppressed the expected P4 inhibition of GTP-gammaS (a G protein activator)-induced contraction and changes in G proteins by downregulating Gi3 and upregulating Gs protein levels. Ch inhibited these P4 actions at the caveolar 3 (CAV-3) level, since the P4 effects were antagonized by treatment with CAV-3 antibody, by reducing CAV-3 expression through CAV-3 siRNA. CAV-3 antibody and siRNA reduced caveolar Ch levels. High caveolar levels of Ch and CAV-3 antibody blocked the incorporation of 3H-P4 into caveolae. Treatment with GDP-betaS (a G protein antagonist) had no effect on P4 actions. High caveolar Ch levels blocked the P4 effects on muscle contraction and G protein changes probably because both Ch and P4 require CAV-3 proteins for their transport across the plasma membrane.

Natriuretic peptides cause relaxation of human esophageal mucosal muscle

Natriuretic peptides have been demonstrated to cause relaxation of the human gallbladder muscle through interaction with natriuretic peptide receptor-B (NPR-B/NPR2). Effects of natriuretic peptides in the human esophageal muscle were unknown. To investigate the effects of natriuretic peptides in the human esophagus, we measured relaxation of muscularis mucosae strips isolated from the human esophagus caused by C-type natriuretic peptide (CNP), brain natriuretic peptide (BNP), atrial natriuretic peptide (ANP) and des[Gln 18, Ser 19, Gly 20, Leu 21, Gly 22]ANP(4-23) amide (cANP(4-23)), a selective natriuretic peptide receptor-C (NPR-C) agonist. In endothelin-1 or carbachol-contracted mucosal muscle strips, CNP caused moderate, sustained and concentration-dependent relaxation. BNP caused a very mild relaxation whereas ANP and cANP(4-23) did not cause any relaxation. CNP was much more potent than BNP and ANP in causing relaxation. These suggest the existence of NPR-B mediating relaxation. The CNP-induced relaxation was not affected by tetrodotoxin or atropine in endothelin-1-contracted esophageal strips and not by tetrodotoxin in carbachol-contracted strips, indicating a direct effect of CNP on the human esophageal muscularis mucosae. Taken together, these results demonstrate that natriuretic peptides cause relaxation of the muscularis mucosae of the human esophagus and suggest that the relaxation is through interaction with NPR-B. Natriuretic peptides may play an important role in the control of human esophageal motility.

Prostaglandins mediate tonic contraction of the guinea pig and human gallbladder

The gallbladder (GB) maintains tonic contraction modulated by neurohormonal inputs but generated by myogenic mechanisms. The aim of these studies was to examine the role of prostaglandins in the genesis of GB myogenic tension. Muscle strips and cells were treated with prostaglandin agonists, antagonists, cyclooxygenase (COX) inhibitors, and small interference RNA (siRNA). The results show that PGE2, thromboxane A2 (TxA2), and PGF(2alpha) cause a dose-dependent contraction of muscle strips and cells. However, only TxA2 and PGE2 (E prostanoid 1 receptor type) antagonists induced a dose-dependent decrease in tonic tension. A COX-1 inhibitor decreased partially the tonic contraction and TxB2 (TxA2 stable metabolite) levels; a COX-2 inhibitor lowered the tonic contraction partially and reduced PGE2 levels. Both inhibitors and the nonselective COX inhibitor indomethacin abolished the tonic contraction. Transfection of human GB muscle strips with COX-1 siRNA partially lowered the tonic contraction and reduced COX-1 protein expression and TxB2 levels; COX-2 siRNA also partially reduced the tonic contraction, the protein expression of COX-2, and PGE2. Stretching muscle strips by 1, 2, 3, and 4 g increased the active tension, TxB2, and PGE2 levels; a COX-1 inhibitor prevented the increase in tension and TxB2; and a COX-2 inhibitor inhibited the expected rise in tonic contraction and PGE2. Indomethacin blocked the rise in tension and TxB2 and PGE2 levels. We conclude that PGE2 generated by COX-2 and TxA2 generated by COX-1 contributes to the maintenance of GB tonic contraction and that variations in tonic contraction are associated with concomitant changes in PGE2 and TxA2 levels.

Natriuretic peptides cause relaxation of human and guinea-pig gallbladder muscle through interaction with natriuretic peptide receptor-B

Atrial natriuretic peptide (ANP) binding sites have been demonstrated in the guinea-pig gallbladder muscle with unclear function. To investigate effects of natriuretic peptides in the gallbladder, we measured relaxation of isolated human and guinea-pig gallbladder strips caused by natriuretic peptides, including C-type natriuretic peptide (CNP), brain natriuretic peptide (BNP) and ANP, as well as des[Gln 18, Ser 19, Gly 20, Leu 21, Gly 22]ANP(4-23) amide (cANP(4-23)), a selective natriuretic peptide receptor-C (NPR-C) agonist. Results in the human gallbladder were similar to those in the guinea-pig gallbladder. CNP, BNP, ANP and cANP(4-23) alone did not cause contraction or relaxation in resting gallbladder strips. However, in carbachol or endothelin-1-contracted strips, CNP caused moderate, sustained and concentration-dependent relaxation. The relaxation was not affected by tetrodotoxin or atropine in endothelin-1-contracted gallbladder strips and not by tetrodotoxin in carbachol-contracted strips. These indicate a direct effect of CNP on the gallbladder muscle. The relative potencies for natriuretic peptides to cause relaxation were CNP>>BNP≥ANP. cANP(4-23) did not cause relaxation. These indicate the existence of the natriuretic peptide receptor-B (NPR-B) mediating the relaxation. Taken together, these results demonstrate that natriuretic peptides cause relaxation of human and guinea-pig gallbladder muscle through interaction with the natriuretic peptide receptor-B.

Endothelin-3 induces both human and opossum gallbladder contraction mediated mainly by endothelin-B receptor subtype in vitro.

Endothelins are produced by gallbladder epithelial cells, suggesting a role in the regulation of gallbladder function. To characterize the effect of endothelin-3 (ET-3) on human and Australian possum gallbladder contractility and identify the receptor(s) involved. Human and possum gallbladder muscle strips were exposed to cumulative concentrations of ET-3 (10 pmol/L-100 nmol/L). Strips were pretreated with either tetrodotoxin (TTX) (1 micro mol/L), the selective ET receptor antagonists BQ-123 (ET(A)), BQ-788 (ET(B)), alone or together, or the mixed ET antagonist tezosentan (all 1 micro mol/L). Maximal changes in tone were measured and expressed as percentage of carbachol (100 micro mol/L)-induced tone. ANOVA was used for statistical analysis. Endothelin-3 induced a concentration-dependent increase in tone in both human and pos-sum strips (P < 0.05) and at 100 nmol/L represented 44.2 +/- 4.5% and 40.3 +/- 4.6% of carbachol-induced tone, respectively. The effect on human strips was TTX insensitive, whereas the possum concentration-response curve was shifted to the right. Individually, BQ-123 and BQ-788 shifted the human concentration-response curve to the right, but a greater inhibition by BQ-788 was achieved in the possum (P < 0.05). However, BQ-123 plus BQ-788 further reduced the ET-3 effect (P < 0.001) to a level comparable to that observed in the presence of tezosentan in both human and possum strips. Endothelin-3 produces potent gallbladder contraction in vitro, acting mainly via ET(B) receptors and also interacting with ET(A)receptors. The receptors are located on the smooth muscle, but in possum gallbladder, neural receptors may also be involved. These findings suggest that ET-3 may regulate motility of possum and human gallbladder.

Active Relaxation of Human Gallbladder Muscle Is Mediated by ATP-Sensitive Potassium Channels

Background: Active and significant relaxation of the human gallbladder must be one of the facets of its motility during both the filling and emptying cycle. Conflicting reports about the presence or significance of nitric oxide have been reported in the literature. The aim of this study was to investigate the role of nitric oxide and K_ATP channels in human gallbladder muscle using isolated strips from human gallbladder. Methods: Full thickness strips were obtained from 56 human gallbladders and suspended under isometric tension in organ baths. The effect of nitric oxide donors and inhibitors on cholecystokinin octapeptide- and carbachol-induced contraction was examined. In separate experiments the effect of the K_ATP channel activator, cromakalim, and the inhibitor, glibenclamide, were determined. Results: Cromakalim induced a significant relaxation of agonist-induced contraction in human gallbladder in vitro, an effect which was abolished by the K_ATP channel inhibitor glibenclamide. No evidence of significant nitric oxide involvement in relaxation was observed. Conclusions: This study has demonstrated the presence of K_ATP channels in human gallbladder for the first time. These are capable of causing significant relaxation in the presence of hormonal and muscarinic agonists and may represent a major pathway for gallbladder relaxation.

Endothelin receptors in human and guinea-pig gallbladder muscle

We measured contraction of muscle strips caused by endothelin (ET) isopeptides and binding of 125I-ET-1 to muscle cell membranes prepared from human and guinea-pig gallbladders. Visualization of 125I-ET-1 binding sites in tissue was performed by autoradiography. Results in human were similar to those in guinea-pig. ET-1 caused tetrodotoxin and atropine-insensitive contraction. The relative potencies for ET isopeptides to cause contraction were ET-1=ET-2>ET-3. ET-1 caused contraction was only slightly inhibited by BQ-123 (potent ET A receptor antagonist) and not by BQ-788 (potent ET B receptor antagonist). It was inhibited by the combination of both. Autoradiography localized 125I-ET-1 binding to the smooth muscle layer. Binding of 125I-ET-1 to muscle cell membranes was saturable and specific. Analysis of dose–inhibition curves demonstrated the presence of two classes of receptors. One class (ET A receptor) had a high affinity for ET-1 and ET-2 but a low affinity for ET-3, and the other (ET B receptor) a high affinity for ET-1, ET-2 and ET-3. These results demonstrate that similar to guinea-pig, human gallbladder possesses both ET A and ET B receptors cooperating to mediate muscle contraction.

Bradykinin induced contraction of human gallbladder muscle in vitro

Aim To examine the mechanisms of Bradykinin (BK)-induced contraction on human gallbladder muscle and to investigate possible receptors that may mediate this action. Methods A full-thickness segment from the anterior aspect of healthy and stone-hearing gallbladders was removed and placed in cold Krebs solution in an organ bath. Concentration-response curves (CRCs) were obtained for BK (0.1-100/LM). The BK response curves were repeated in the presence of a number of antagonists and channel blockers BI & B2 receptor antagonists, SR 27897 (0.5nM,a CCK-A receptor antagonist), mepyramine (l/LM, a histamine receptor antagonist), atropine (l/LM, a muscarinic receptor antagonist), prazosin (O.l/LM,a adrenoceptor blocker), tetrodotoxin (O.03/LM, a Na channel blocker), quinidine (l/LM, a K channel blocker) and indomethacin (3/LM, a cyclo-oxygenase inhibitor). Extracellular Ca involvement was examined by use of Ca free medium. Ryanodine (lO/LM) was used to examine intracellular involvement. Ethics committee approval for tissue sampling was obtained. Statistical significance was performed using t-test, P < .05 or less was considered as indicative of significance. Results Healthy (n=6) and stone-bearing (n=9) gallbladders showed similar and repeatable CRCs to BK (EDso=4.95 & 5.5/LM). The BK response was significantly reduced only in healthy strips by BI receptor blockade (EDso=31.5/LM) and in both tissue types by B2 receptor blockade (EDso=37.2 & 29./LM). Neither antagonist affected the maximum BK response. No significant rightward shift of the response to BK was observed in the presence of mepyramine (n=4), atropine (n=), prazosin (n=6), tetrodotoxin (n=), quinidine (n=7) or SR27897 (n=5). A significant rightward shift of the curve was noted in the presence of indomethacin (n=20,EDso=55/LM). BK-induced contraction was not modified in Ca-free medium (n=7), however the presence of ryanodine caused a significant rightward shift of the BK dose-response curve (n=7,EDso=46/LM. Conclusion Gallbladder strips contract to BK in a dose-dependent manner. A difference in receptor population seems to exist between normal and stone-bearing gallbladders. BK appears to have a direct myogenic effect on the human gallbladder and this may be mediated by a third BK receptor or a BK-independent mechanism. The contraction occurs independently of extracellular Ca but intracellular Ca is vital. In addition, part of this BK-induced contraction is probably mediated by the release of a cyclo-oxygenasc-dcrived product from the arachidonic acid pathway.

Excess membrane cholesterol alters human gallbladder muscle contractility and membrane fluidity

Background & Aims: The relationship between muscle contractility, plasma membrane cholesterol, and fluidity was investigated in human gallbladders with gallstones. Methods: Isolated gallbladder muscle cells were used to measure contraction. Plasma membranes of gallbladder muscle were purified in a sucrose gradient and measured for cholesterol content and cholesterol/phospholipid mole ratio. Membrane fluidity was determined by using fluorescence polarization and was expressed as the reciprocal of anisotropy. Results: The maximal contraction induced by cholecystokinin octapeptide was significantly less in gallbladders with cholesterol stones than in those with pigment stones. The membrane cholesterol content and cholesterol/phospholipid mole ratio were significantly higher in gallbladders with cholesterol stones than in those with pigment stones. Membrane anisotropy was also higher than in gallbladders with pigment stones, reflecting lower membrane fluidity in gallbladders with cholesterol stones. After muscle cells from cholesterol stone gallbladders were incubated with cholesterol-free liposomes for 4 hours, cholecystokinin octapeptide–induced contraction, membrane cholesterol content and cholesterol/phospholipid ratio, and membrane fluidity returned to normal levels. Conclusions: Gallbladder muscle from patients with cholesterol stones has increased membrane cholesterol/phospholipid mole ratio and decreased membrane fluidity resulting in impaired muscle contractility. These abnormalities are corrected by removing the excess cholesterol from the plasma membranes. GASTROENTEROLOGY 1999;116:678-685

Excess membrane cholesterol alters CCK receptor binding affinity and capacity of human gallbladder muscle

Excess membrane cholesterol alters CCK receptor binding affinity and capacity of human gallbladder muscle

Effect of the nitric oxide donor, glyceryl trinitrate, on human gall bladder motility

Background—Nitric oxide is a major neurotransmitter in non-adrenergic, non-cholinergic (NANC) pathways. NANC inhibitory innervation has been shown in human gall bladder muscle in vitro; the role of nitric oxide in...

Gallbladder relaxation in patients with pigment and cholesterol stones

BACKGROUND & AIMS: Gallbladders with cholesterol stones show a defective contraction in response to agonists. The aim of this study was to investigate the muscle relaxation of human gallbladders with cholesterol or black pigment gallstones. METHODS: Gallbladder relaxation was measured in vitro using muscle strips and single muscle cells. Relaxation was expressed as percent inhibition of either basal active tension in strips or maximal cell contraction induced by diacylglycerol. The production of cyclic nucleotides was determined using a 125I-labeled radioimmunoassay kit. RESULTS: Frequency-dependent relaxation evoked by electrical field stimulation was significantly lower in gallbladders with cholesterol stones than in gallbladders with pigment stones. Relaxation and adenosine 3',5'-cyclic monophosphate (cAMP) production induced by isoproterenol, vasoactive intestinal peptide, and forskolin were also significantly decreased in gallbladders with cholesterol stones. However, the relaxation in response to 8-bromo-cAMP, nitric oxide (NO), and the NO donor S-nitroso- N-acetylpenicillamine (SNAP), which circumvent plasma membrane receptors and directly activate intracellular mechanisms, was similar in gallbladders with cholesterol and pigment stones. Guanosine 3',5'- cyclic monophosphate production induced by NO and SNAP was also similar. CONCLUSIONS: Human gallbladder muscle from specimens with cholesterol stones show an impaired relaxation and lower cAMP production compared with specimens with pigment stones. The muscle defect(s) responsible for this impairment seem to be in the plasma membranes. (Gastroenterology 1997 Sep;113(3):930-7)

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 125I-Bolton-Hunter sulfated CCK octapeptide (125I-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 125I-BH-CCK-8 to the pancreas was inhibited by agonists with the affinities (dissociation constant) of CCK (0.11 nmol/L) approximately 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 125I-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 sub-types 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. (Gastroenterology 1996 Dec;111(6):1621-6)

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

Abstract 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 125I-Bolton-Hunter sulfated CCK octapeptide (125I-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 125I-BH-CCK-8 to the pancreas was inhibited by agonists with the affinities (dissociation constant) of CCK (0.11 nmol/L) approximately 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 125I-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 sub-types 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. (Gastroenterology 1996 Dec;111(6):1621-6)

In vitro contractility of stimulated and non‐stimulated human gallbladder muscle

In an attempt to define, more clearly, the nature of gallbladder contraction we obtained muscle strips from human gallbladder wall, removed at cholecystectomy. Samples were taken from various areas of the gallbladder to seek evidence of a dominant axis of contraction. The strips were stimulated with increasing concentrations of cholecystokinin-8 (CCK-8) and carbachol, and, to determine maximal contractile force, 0.25 M potassium chloride. No differences were seen between samples taken from the long-itudinal, circular and oblique axes. In a second series of experiments, samples were taken from the body and neck regions of the gallbladder. In these, it was seen that the samples from the body contracted more forcefully than those of the neck tissue and that they were more sensitive to carbachol stimulation. The difference in response to CCK-8 measured in the strips from the body and cystic duct/neck of the gallbladder cannot be explained by a difference in sensitivity to CCK-8, but is mainly due to the difference in the amount of muscle tissue present. Strips from the body are more sensitive to muscarinic stimulation that those from the neck. Overall, there is a functional difference in sensitivity between the body and neck which would serve to facilitate bile flow into the common bile duct during gallbladder contraction.

Impaired Release of Gallbladder Calcitonin Gene-Related Peptide in Human Gallstone Disease

Calcitonin gene-related peptide (CGRP) is a neurotransmitter present in the peripheral ends of sensory neurons of the gut and may modulate reflexes of the enteric nervous system. We studied the release of CGRP in normal human gallbladders and in those containing gallstones to test the hypothesis that abnormalities of regulation of CGRP release participate in gallstone formation. Human gallbladder strips were obtained from histologically normal organs removed during liver surgery ( n = 8) or from patients operated upon for symptomatic cholelithiasis ( n = 14). After removal of the mucosa, muscle strips were superfused with oxygenated Kreb's buffer in an organ bath at 37°C. Pharmacologic agents were added to the superfusate and samples were collected at 2-min intervals for analysis. CGRP release was measured by a sensitive and specific radioimmunoassay and adjusted for tissue weight. In normal gallbladders, CGRP release was stimulated sixfold over basal by capsaicin (10 -5 M) to 363 ± 75 pg per gram of muscle per 2 min. This release was abolished by addition of somatestatin (SS) or the neural blocker tetrodotoxin (TTX). Lesser degrees of CGRP release were observed after nonspecific stimulation with K + or phosphodiesterase inhibition with caffeine. In gallbladders with gallstones, capsaicin-induced CGRP release was 74 ± 16 pg per gram of muscle per 2 min (20% of normal, P < 0.001). Release induced by caffeine and K + was also inhibited compared to normal gallbladder strips. Release of CGRP from diseased strips was abolished by TTX and inhibited by SS to degrees similar to normal tissue. CGRP release in normal human gallbladder muscle strips is increased by the sensory neuron stimulant capsaicin, the nonspecific stimulant K +, and phosphodiesterase inhibition by caffeine. This release is abolished by blockade of axonal transmission with TTX and by SS. CGRP content and release from gallbladders containing gallstones are inhibited. Whether these observations have significance in gallstone formation or are secondary processes remains to be seen.

Impaired IP3 and dag production in human gallbladder muscle with cholesterol stones

Impaired IP3 and dag production in human gallbladder muscle with cholesterol stones