Contraction Of Human Gallbladder Research Articles

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.

Genistein Aglycone is Effective in Reducing Bone Loss and Some Predictors of Cardiovascular Risk in Postmenopausal Women: A 3-Years Study

To investigate the mechanisms controlling human gallbladder contraction, especially to determine the role of neural factors, the gallbladder response to various stimuli was evaluated in eight normal subjects using realtime ultrasonography. In addition, plasma cholecystokinin (CCK) levels were measured using a region-specific antibody (OAL 656). Intramuscular injections of CCK-8 and of cerulein induced mean maximal ejection fractions (EF max) of 50% ± 6% and 58% ± 4%, respectively. The mean EF max after ingestion of a fatty meal was 44% ±3%, while the EF max after a fat- restricted meal was significantly lower (17% ±4%). Oral water and sham feeding also significantly induced gallbladder contractions (EF max; 25% ±4% and 12% ±4% respectively) that were eliminated by premedication with atropine. The plasma CCK rose significantly after exogenous administration of CCK-8 and after ingestion of a fatty meal. The peak CCK concentration released after fatty meals was almost identical to that after exogenous CCK-8 loading. In contrast, plasma CCK levels showed no change after the fat-restricted meal, oral water and sham feeding. These findings suggest that not only CCK but also the cholinergic pathway may play important roles in the control mechanism of human gallbladder contraction.

Duodenal phytohaemagglutinin (red kidney bean lectin) stimulates gallbladder contraction in humans

Lectins, carbohydrate-specific proteins without enzymatic activity on the ligand, are daily ingested plant proteins which survive the passage through the gastrointestinal tract in a biologically active form. Their binding to glycan determinants of natural glycoconjugates can trigger biological effects. The lectin phytohaemagglutinin (PHA) is abundantly present in red kidney beans and induces cholecystokinin (CCK) release in rats. The aim of the study was to investigate the effect of intraduodenal administration of PHA on plasma CCK levels and gallbladder contraction in humans and to elucidate potential mechanisms of action. Five healthy volunteers underwent four studies. After a basal intraduodenal saline infusion for 30 min, PHA or heat-inactivated PHA was infused in increasing doses: 150 microg, 1.5 mg and 15 mg for 30 min each. Intravenous saline, CCK(1) receptor antagonist dexloxiglumide or atropine were administered in random order. Gallbladder volumes were measured by ultrasonography and plasma CCK levels by radioimmunoassay. Intraduodenal PHA induced gallbladder contraction in a dose-dependent fashion starting with the lowest dose. The highest dose reduced the gallbladder volume to 65.3 +/- 9.4% of basal volume (P < 0.001) whereas heat-inactivated PHA did not have any effect. Blocking CCK(1) or muscarinic receptors completely abolished PHA-stimulated gallbladder contraction (dexloxiglumide 208.7 +/- 23.7%; atropine 104 +/- 7.0% of basal volume) while none of the treatments affected CCK levels. Duodenal administration of PHA potently stimulates gallbladder contraction in humans. This contraction is mediated via cholinergic pathway.

Unexpected relationship between plasma protein binding and the pharmacodynamics of 2‐NAP, a CCK1‐receptor antagonist

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT?: * Two chemically diverse CCK1 receptor antagonists have been shown clinically to inhibit CCK-evoked contraction of human gallbladder [2, 3]. These studies have not examined the relationship between plasma concentration and effect, the latter usually considered to be predictive from the free drug concentration [8]. * We wanted to examine our novel CCK1 receptor antagonist in this validated model and also to explore its PK-PD relationship. * 2-NAP inhibited CCK-evoked human gallbladder contraction in vivo but at a plasma free concentration that was, in theory, too low to have achieved adequate CCK1 receptor occupancy. * The study serves as a caveat to the assumption that free plasma concentration can be used to predict pharmacological effect. To study the pharmacokinetics and pharmacodynamics of 2-NAP (2-naphthalenesulfonyl-L-aspartyl-(2-phenethyl)amide), a selective CCK1 receptor antagonist in healthy volunteers. 2-NAP was given to 12 healthy male volunteers in an ascending dose, safety and PK phase 1a study by 1 h i.v. infusion (0.6-9.6 mg kg(-1) h(-1)). A further 12 healthy male volunteers received i.v. CCK-8S (6.25 pmol kg(-1) h(-1)) to produce gallbladder contraction, measured by ultrasound recordings of gallbladder volume, and the effect of concurrent i.v. 2-NAP administration was studied. Plasma protein binding in vitro and ex vivo was measured by ultrafiltration and by equilibrium dialysis. 2-NAP was generally well tolerated, displayed linear pharmacokinetics and a very high degree of plasma protein binding (99.9%). A 105 min i.v. CCK-8S infusion induced a reduction in gallbladder volume of 14.9 (+/-7.0) ml during placebo co-infusion and this was reduced to 2.4 (+/-5.9) ml when 2-NAP was co-infused with CCK-8S (P = 0.00024, paired t-test, mean change 12.5 ml; 95% CI For mean 7.4, 18.3 ml). This extent of inhibition was consistent with a 2-NAP total plasma concentration of 36 microm, but when protein binding corrections were made, the 'free concentration' of 2-NAP was only 0.04 microm, a value much less than the average equilibrium dissociation constant of 2-NAP for human CCK1 receptors ( approximately 0.7 microm). The pharmacological effect of a drug is usually considered to be determined by its free concentration. However, the complete inhibition of CCK-8S-evoked gallbladder contraction by a free plasma concentration of 0.04 microm 2-NAP was much greater than would have been predicted from simple drug-receptor occupancy theory and cautions against the general use of free concentration of drug for predicting pharmacological effect.

Pharmacological characterization of cholecystokinin receptors mediating contraction of human gallbladder and ascending colon

Cholecystokinin (CCK) produces contractions of gallbladder and colon in a number of different species. Although the effects of CCK on the human gallbladder are relatively well documented, the CCK receptors in the human colon have not been clearly characterised. Therefore, in this study, the CCK receptors in the human gallbladder and colon were compared using pharmacological techniques. Contraction of specimens of the human tissue was measured using in vitro organ bath bioassay. The effect of selective concentrations of CCK 1 and CCK 2 receptor antagonists (L-364,718 and JB93182, respectively) was determined on agonist concentration–effect ( E/[ A]) curves obtained by cumulative dosing with sulphated CCK. The CCK 1 antagonist L-364,718 produced a rightward shift of the CCK-8S [ E/[ A] curve in the human gallbladder (p A 2=9.15±0.26) and ascending colon (p A 2=9.20±0.33). In both tissues, the CCK 2 receptor antagonist, JB93182, had no effect on the CCK E/[ A] curves. In addition, in the colon, pentagastrin responses were inhibited by L-364,718 but unaffected by JB93182. These data indicate that the CCK-induced contraction of the human colon and gallbladder smooth muscle is mediated solely through the CCK 1 receptor subtype, and the antagonist affinity estimates are consistent with those previously obtained in experiments on animal tissue.

Stimulation of gallbladder emptying by intravenous lipids.

Few studies have dealt with the effect of i.v. administration of lipids on gallbladder emptying, and the results have been conflicting. Five healthy volunteers, three women and two men, aged 26 to 54 years, (mean, 29 years) were studied. Gallbladder emptying was assessed by means of real-time ultrasonography. In all subjects, the infusion of a 10% fat emulsion (Intralipid; Kabivitrum, Stockholm) over 3 hours caused a reduction in gallbladder volume. This effect was statistically significant at about 80 minutes of lipid infusion and became progressively more marked as the infusion progressed, reaching a reduction of approximately 30% during the third hour of infusion. A significant relationship (p < .001) was found between the concentration of serum triglycerides and the degree of gallbladder volume decrease. In control studies, infusion of physiologic saline containing glycerol, the excipient of intralipid, caused no significant changes in gallbladder volume. The results indicate that i.v. infusion of lipids is able to stimulate significantly contraction of human gallbladder.

Intraduodenal free fatty acids rather than triglycerides are responsible for the release of CCK in humans.

Exocrine pancreas from different species behaves differently in response to the presence of intact or digested nutrients in the duodenum. A failure of cholecystokinin (CCK) release after a meal has been shown among patients with exocrine pancreatic insufficiency. This abnormality could be restored by the administration of pancreatic extracts, suggesting that digested rather than intact nutrients are responsible for the release of CCK and subsequently gallbladder contraction in humans. The aim of this study was to determine the specific role of different lipidic stimuli in humans. Seven male patients (mean age, 52 years) with pancreatic insufficiency secondary to chronic pancreatitis were selected. Pancreatic insufficiency was considered severe in five of them (lipase output, < 1,000 IU/min) and moderate in another two (lipase output, > 1,000 and < 2,300 IU/min). Plasma CCK (by bioassay), gallbladder contraction (by ultrasound), and enzyme output (chymotrypsin) in response to duodenal administration of either oleic acid as free fatty acids or 20% Intralipid as triglycerides were measured in each patient with at least a 48-h interval between each test. In all these patients with pancreatic insufficiency, duodenal perfusion of free fatty acids generated a more pronounced (91 +/- 11 vs. 49 +/- 21 pM) and faster (15 vs. 30 min) (p < 0.05) CCK release than triglycerides. Furthermore, gallbladder contraction was more efficient when free fatty acids instead of triglycerides were administered in the duodenum (86 +/- 5 vs. 69 +/- 4%) at 10 min (p < 0.05) and (73 +/- 8 vs. 51 +/- 5%) at 15 min (p < 0.03). Among patients with measurable residual pancreatic function, enzyme outputs were shown to be higher during free fatty acid than triglyceride perfusion. In humans, free fatty acids rather than triglycerides, when present in the duodenum, stimulate CCK release and gallbladder contraction. In patients with moderate pancreatic insufficiency this phenomenon may increase residual enzymatic secretion. These results allow us to encourage the development of enzymatic preparations as acid-resistant lipases that cause a fast release of free fatty acids in the duodenum.

Effect of oral erythromycin on gallbladder motility in normal subjects and subjects with gallstones

The action of the motilin receptor agonist erythromycin on human gallbladder contraction, measured by ultrasound, both in normal subjects and those with gallstone disease was studied. In 17 normal subjects, oral erythromycin administration (500 mg; vs. placebo) reduced fasting gallbladder volume at 2 hours (26.2 vs. 19.0 mL; P < 0.001), and postprandial residual gallbladder volume (9.0 vs. 4.4 mL; P < 0.001) and the rate constant of gallbladder emptying following the meal was significantly increased. Erythromycin also reduced fasting and residual gallbladder volumes in 13 patients with gallstone disease: in 6 who underwent cholecystolithotomy, fasting volume was 29.5 vs. 22.3 mL (P < 0.05) and residual volume was 17.7 vs. 6.5 mL (P < 0.05), and in 7 with gallstones in situ, fasting volume was 23.8 vs. 14.3 mL (P < 0.05) and residual volume was 17.2 vs. 5.0 mL (P < 0.05). In 7 of 8 subjects with gallstones and impaired gallbladder emptying, the gallbladder emptied normally following administration of erythromycin, and in 3 of the other 5 gallstone subjects gallbladder emptying was increased. In 6 normal subjects given erythromycin three times weekly for 1 month, the effect was maintained (fasting volume, 18.8 mL, P < 0.001; residual volume, 3.7 mL, P < 0.001). Oral erythromycin significantly reduces fasting and postprandial residual gallbladder volumes in both normal subjects and subjects with gallstones and reverses the gallbladder motility defect found in a proportion of subjects with gallstones. This effect is maintained for a month in normal subjects.

Coffee stimulation of cholecystokinin release and gallbladder contraction in humans

We studied the effect of the ingestion of 400 mL regular coffee on plasma cholecystokinin (CCK) concentrations and of 165 mL regular and decaffeinated coffee on plasma CCK and gallbladder contraction in six healthy regular coffee drinkers. Plasma CCK concentrations rose 3.3 +/- 0.4 pmol/L after 400 mL and 2.8 +/- 0.9 pmol/L after 165 mL regular coffee compared with 1.8 +/- 0.6 pmol/L after 165 mL decaffeinated coffee. These plasma CCK increments were greater than those after 400 and 165 mL of an isosmotic and isothermic sodium chloride solution (0.6 +/- 0.2 and 0.4 +/- 0.1 pmol/L, respectively). An average gallbladder contraction of 33 +/- 7% was observed after 165 mL regular coffee and 29 +/- 10% after 165 mL decaffeinated coffee, whereas after 165 mL sodium chloride the contraction was only 10 +/- 12%. We conclude that both regular coffee and decaffeinated coffee give rise to increments in plasma CCK and contractions of the gallbladder.

Intravenous amino acids stimulate human gallbladder emptying and hormone release

Gallbladder stasis during prolonged total parenteral nutrition (TPN) has been documented. We have examined the effect of intravenous amino acid infusion on human gallbladder contraction and release of cholecystokinin (CCK). Five healthy adult volunteers were given amino acid infusions at different rates (65, 125, 240, and 600 mg.kg-1.h-1). The volume of the gallbladder was calculated by means of ultrasonographic measurements. Plasma samples were analyzed for CCK immunoreactivity. Gallbladder and hormone responses after intravenous amino acids were compared with responses after a fat meal, after a protein meal, and after ingestion of an oral amino acid mixture. We found that intravenous amino acids stimulated human gallbladder contraction in a dose-related manner. The mechanism of stimulation may be through the release of CCK although significant correlation was not demonstrated. The magnitude of response is similar to that seen after meal stimulation. To compare the delivery of amino acids during a standard meal and during each dose of intravenous amino acids, peripheral plasma levels of dietary amino acids were measured after a standard commercially prepared enteral supplement meal and after each dose of intravenous amino acids. Our lower doses of amino acid infused resulted in levels of circulating amino acid comparable to those after a meal. The induction of gallbladder contraction and release of CCK in human recipients of parenteral nutrition may be of value in some circumstances.

VIP does not effect CCK-induced human gallbladder contraction

VIP does not effect CCK-induced human gallbladder contraction

Gallbladder Dynamics and Plasma Cholecystokinin Responses After Meals, Oral Water, or Sham Feeding in Healthy Subjects

To investigate the mechanisms controlling human gallbladder contraction, especially to determine the role of neural factors, the gallbladder response to various stimuli was evaluated in eight normal subjects using realtime ultrasonography. In addition, plasma cholecystokinin (CCK) levels were measured using a region-specific antibody (OAL 656). Intramuscular injections of CCK-8 and of cerulein induced mean maximal ejection fractions (EF max) of 50% +/- 6% and 58% +/- 4%, respectively. The mean EF max after ingestion of a fatty meal was 44% +/- 3%, while the EF max after a fat-restricted meal was significantly lower (17% +/- 4%). Oral water and sham feeding also significantly induced gallbladder contractions (EF max; 25% +/- 4% and 12% +/- 4% respectively) that were eliminated by premedication with atropine. The plasma CCK rose significantly after exogenous administration of CCK-8 and after ingestion of a fatty meal. The peak CCK concentration released after fatty meals was almost identical to that after exogenous CCK-8 loading. In contrast, plasma CCK levels showed no change after the fat-restricted meal, oral water and sham feeding. These findings suggest that not only CCK but also the cholinergic pathway may play important roles in the control mechanism of human gallbladder contraction.

Cephalic Stimulation of Gallbladder Contraction in Humans: Role of Cholecystokinin and the Cholinergic System

To determine the role of cholecystokinin and the cholinergic system in cephalic stimulation of gallbladder contraction and to compare the degree of gallbladder contraction by cephalic stimulation with postprandial gallbladder contraction, 8 healthy volunteers (4 males, 4 females, 20-65 years) underwent the following studies: sham feeding of an appetizing meal, sham feeding with intravenous atropine, and ingestion of the same meal. Gallbladder volume was measured by real-time ultrasonography and plasma cholecystokinin by a sensitive and specific radioimmunoassay using antibody T204. Gallbladder contraction in response to sham feeding, 30 +/- 4% (p = 0.0001 vs. basal), amounted to half of that seen after real feeding, 69 +/- 5% (p less than 0.0001 vs. basal). Significant dissociation between gallbladder response to sham feeding and real feeding was seen from 40 min (p less than 0.005-p = 0.0001). Atropine did not affect basal gallbladder volume but completely abolished gallbladder contraction in response to sham feeding. Neither sham feeding without nor sham feeding with atropine significantly affected plasma cholecystokinin levels. On the other hand, real feeding induced significant increases in plasma cholecystokinin from a basal level of 2.3 +/- 0.1 pM to a peak value of 5.9 +/- 0.4 pM at 40 min. It is concluded that an important cephalic phase of postprandial gallbladder contraction exists which is cholecystokinin-independent but dependent on a cholinergic mechanism.

Gallbladder Emptying in Response to Cholecystokinin

The threshold and dynamics of gallbladder emptying in human subjects in response to cholecystokinin (Pancreozymin, Boots Co. Ltd) were defined by radionuclide imaging with a gamma camera. The radiopharmaceutical employed, 99mTc-HIDA, was taken up rapidly by the liver and efficiently excreted into the biliary system so that gallbladder filling was easily distinguishable from negligible background activity. Counts were recorded continuously on magnetic tape during i.v. infusion of sequentially increasing doses of cholecystokinin: Each dose level was maintained for 15 min. At later playback, the area of interest was adjusted to include only the gallbladder and to exclude radioactivity present in the gut during gallbladder emptying. In 19 normal subjects (10 male and 9 female), a threshold dose of cholecystokin was identified for gallbladder contraction: 0.010 Crick-Harper-Raper units/kg-min in 16 subjects, and 0.020 Crick-Harper-Raper units/kg-min in the remaining 3. The rate of emptying appeared smooth and linear at each dose level: Doubling the dose of cholecystokinin in every case significantly increased the emptying rate. There appeared to be no effect of increasing age on emptying more rapidly than females, but the difference was not significant. This cholescintigraphic technique would appear to offer a simple, accurate, yet noninvasive method for continuously monitoring the events during gallbladder contraction in humans.