Vagal blocking improves glycemic control and elevated blood pressure in obese subjects with type 2 diabetes mellitus.

BACKGROUND: An active device that downregulates abdominal vagal signalling has resulted in significant weight loss in feasibility studies. OBJECTIVE: To prospectively evaluate the effect of intermittent vagal blocking (VBLOC) on weight loss, glycemic control, and blood pressure (BP) in obese subjects with DM2. METHODS: Twenty-eight subjects were implanted with a VBLOC device (Maestro Rechargeable System) at 5 centers in an open-label study. Effects on weight loss, HbA1c, fasting blood glucose, and BP were evaluated at 1 week to 12 months. RESULTS: 26 subjects (17 females/9 males, 51 ± 2 years, BMI 37 ± 1 kg/m(2), mean ± SEM) completed 12 months followup. One serious adverse event (pain at implant site) was easily resolved. At 1 week and 12 months, mean excess weight loss percentages (% EWL) were 9 ± 1% and 25 ± 4% (P < 0.0001), and HbA1c declined by 0.3 ± 0.1% and 1.0 ± 0.2% (P = 0.02, baseline 7.8 ± 0.2%). In DM2 subjects with elevated BP (n = 15), mean arterial pressure reduced by 7 ± 3 mmHg and 8 ± 3 mmHg (P = 0.04, baseline 100 ± 2 mmHg) at 1 week and 12 months. All subjects MAP decreased by 3 ± 2 mmHg (baseline 95 ± 2 mmHg) at 12 months. CONCLUSIONS: VBLOC was safe in obese DM2 subjects and associated with meaningful weight loss, early and sustained improvements in HbA1c, and reductions in BP in hypertensive DM2 subjects. This trial is registered with ClinicalTrials.gov NCT00555958.

Remission of diabetes in patients with long-standing type 2 diabetes following placement of adjustable gastric band: a retrospective case control study.

Rates of remission in obese patients with long-standing type 2 diabetes (>2 years), following an adjustable gastric band are unclear. We conducted a retrospective case-control study of patients (n = 89) matched for age and body mass index with non-surgical controls. Cases had a longer duration of diabetes (99 ± 53 and 80 ± 59 months, p < 0.05) and a lower HbA1c than controls (7.9 ± 1.6 vs. 8.5 ± 1.9%, p < 0.05). At follow-up (median 105 weeks) cases had lost 16.8 ± 13.5 kg and controls 1.7 ± 8.9 kg (p < 0.001) and HbA1c decreased by 0.6-0.8% (p < 0.001 for time) with no difference between cases and controls. Diabetes resolution, defined by HbA1c less than 6.5% and taking no medications, occurred in 14 (16%) cases and 2 controls. This is in contrast to published outcomes of resolution of type 2 diabetes after bariatric surgery. We conclude that there is a clear need for randomized studies of the effect of gastric banding in patients with long-standing type 2 diabetes.

Galanin receptor 3--a potential target for acute pancreatitis therapy.

BACKGROUND: Galanin participates in the pathogenesis of acute pancreatitis (AP). The galanin receptor (GALR) sub-types involved, however, are unclear. We aimed to determine GALRs messenger RNA (mRNA) expression in mouse pancreas, describe their localization, and ascertain if GALR2 and GALR3 are involved in AP. METHODS: Galanin receptor expression in murine whole pancreas, acinar, and islet cells was quantified by polymerase chain reaction amplification of reverse-transcribed RNA for mRNA, Western blot analysis for protein and in situ hybridization for GALR localization. Isolated acinar cells were used to determine galanin's effect on amylase secretion. Acute pancreatitis was induced in mice by caerulein injections. Mice, with and without AP, were treated with the highly selective GALR2 antagonist M871, or the specific GALR3 antagonist SNAP-37889. Indices of AP were measured at 12 h. KEY RESULTS: Murine pancreas expresses mRNA for GALRs. In islets the expression of all GALR are comparable, whereas in acinar cells GALR3 is predominantly expressed. Western blot analysis confirmed that the GALR proteins are expressed by acinar cells. In situ hybridization analysis confirmed that GALR3 mRNA is present in islet and acinar cells, while mRNA for GALR1 and 2 is confined to islets. Galanin did not influence basal and caerulein-stimulated amylase release from acinar cells. M871 treatment reduced some, whereas SNAP-37889 treatment reduced all indices of AP (by 40-80%). CONCLUSIONS & INFERENCES: Galanin receptor mRNA and protein are expressed in mouse pancreas, with GALR3 mRNA predominating. GALR3 antagonism reduced the severity of AP whereas GALR2 antagonism was less effective. GALR3 is a potential target for treatment of AP.

Galanin receptor antagonist m35 but not m40 or c7 ameliorates cerulein-induced acute pancreatitis in mice.

BACKGROUND/AIMS: We compared the galanin antagonists C7, M35, M40 and galantide, for their ability to ameliorate acute pancreatitis (AP). METHODS: Galanin antagonists were co-administered with 7 hourly cerulein injections used to induce AP. Plasma amylase and lipase activities were measured as indices of AP, and pancreata were harvested at 12 h for histological examination and estimation of myeloperoxidase (MPO) activity. RESULTS: Treatment with galantide, M35 and C7 ameliorated the AP-induced plasma hyperenzymemia by 40-75%. Administration of M40 did not significantly alter plasma hyperenzymemia. Galantide, M35 and M40 significantly reduced the pancreatic MPO activity by 65-80%, whereas C7 increased MPO activity. Galantide and M35 but not C7 or M40 treatment significantly reduced the AP-induced necrosis score by 30-50% compared to the AP alone group. C7 alone increased plasma lipase activity and the pancreatic necrosis score compared with saline treatment alone, whereas the other antagonists were without effect. CONCLUSION: Galantide and M35 ameliorated the severity of AP, but M40 and C7 had mixed effects. Complex galanin pathways may be involved in cerulein-induced AP. M35 and galantide are potential therapeutic peptides for the treatment of AP and further evaluation should be considered. and IAP.

Intra-abdominal vagal blocking (VBLOC therapy): clinical results with a new implantable medical device.

BACKGROUND: A new medical device uses high-frequency electrical algorithms to create intermittent vagal blocking (VBLOC therapy). The aim is to assess the effects of vagal blocking on excess weight loss (EWL), safety, dietary intake, and vagal function. METHODS: An open-label, 3-center study was conducted in obese subjects (body mass index [BMI] 35-50 kg/m(2)). Electrodes were implanted laparoscopically on both vagi near the esophagogastric junction to provide electrical block. Patients were followed for 6 months for body weight, safety, electrocardiogram, dietary intake, satiation, satiety, and plasma pancreatic polypeptide (PP) response to sham feeding. To specifically assess device effects alone, no diet or exercise programs were instituted. RESULTS: Thirty-one patients (mean BMI, 41.2 +/- 1.4 kg/m(2)) received the device. Mean EWL at 4 and 12 weeks and 6 months after implant was 7.5%, 11.6%, and 14.2%, respectively (all P < .001); 25% of patients lost >25% EWL at 6 months (maximum, 36.8%). There were no deaths or device-related serious adverse events (AEs). Calorie intake decreased by >30% at 4 and 12 weeks and 6 months (all P 25 pg/mL (P = .02). Three patients had serious AEs that required brief hospitalization, 1 each for lower respiratory tract, subcutaneous implant site seroma, and Clostridium difficile diarrhea. CONCLUSIONS: Intermittent, intra-abdominal vagal blocking is associated with significant EWL and a desirable safety profile.

A novel preparation to study rat pancreatic spinal and vagal mechanosensitive afferents in vitro.

The management of pancreatic pain is a significant clinical problem so understanding of how sensory signals are generated in pancreatic tissue is fundamental. We aimed to characterize mechanosensitive and chemosensitive properties of pancreatic spinal and vagal afferents in vitro. Spinal and vagal afferent preparations from Sprague-Dawley rats were established incorporating the left splanchnic nerve or vagus nerves respectively. The common bile duct was cannulated for distension of the pancreatic duct with fluid. Nerve discharge evoked by blunt probing, duct distension or electrical stimulation was obtained from teased nerve bundles using standard extra-cellular recording. Discharge from 197 spinal afferent bundles was recorded, of which 57% displayed spontaneous activity. Blunt probing revealed 61 mechanosensitive receptive fields which were associated primarily with arteries/blood vessels (33/61) and the parenchyma (22/61). All mechanosensitive responses were slowly adapting, with 33% continuing to discharge after termination of the stimulus and 60% displaying a response threshold <10 g. Application of chemical mediators (bradykinin, histamine, 5-hydroxytryptamine, cholecystokinin octapeptide) evoked a response from 31/57 units, with 33% excitatory and 23% inhibitory. Spontaneous discharge was recorded from 72% of 135 vagal bundles. Mechanosensitive receptive fields were not identified in the pancreas but were evident in adjacent organs. No spinal or vagal afferent response to duct distension was obtained. In conclusion, pancreatic mechanosensitive spinal afferents are common, in contrast to pancreatic mechanosensitive vagal afferents indicating that pancreatic sensory innervation is predominantly spinal. Chemosensitive spinal afferent nerve endings are present in the pancreas and respond to a variety of inflammatory and physiological mediators.

Associates of change in liver fat content in the morbidly obese after laparoscopic gastric banding surgery.

AIM: Hepatic steatosis affects up to 30% of the population. After weight loss, monitoring of the change in hepatic steatosis is not routinely performed. This study aimed to define the closest associates of change in liver fat content in a population of obese females following laparoscopic gastric banding surgery. METHODS: Before and 3 months after surgery, proton magnetic resonance spectroscopy and magnetic resonance imaging were used to estimate the amount of lipid contained within the liver and abdominal subcutaneous and visceral compartments of 29 obese [mean body mass index (BMI) 39 +/- 5 kg/m(2)], non-diabetic women aged between 20 and 62 years. Liver enzymes, fasting plasma glucose and insulin were also measured as well as body weight, BMI and waist circumference. Insulin sensitivity was estimated using homeostasis model assessment insulin resistance index. RESULTS: Significant reductions occurred in body weight (p < 0.001), abdominal fat volumes (p < 0.001) and liver fat (p = 0.037) 3 months after surgery. Change in liver fat content more closely associated with change in serum gamma-glutamyl transferase (GGT; r = 0.71, p < 0.001) than with changes in weight (r = 0.10, p = 0.612) and waist circumference (r = 0.15, p = 0.468). CONCLUSIONS: Our findings suggest that obese non-diabetic female patients who have undergone significant weight loss over 3 months can be better assessed for the regression of excess liver fat content by monitoring changes in serum GGT levels rather than changes in simple anthropometry.

Selective iNOS inhibition enhances spontaneous gallbladder motility in the Australian possum.

Gallbladder inflammation is a common and painful disease. Inducible nitric oxide synthase (iNOS) plays a major role in inflammatory diseases, and iNOS inhibitors are being developed as therapeutic agents. Reports are inconsistent regarding iNOS expression in normal gallbladder. The aim of this study was to determine the effect of iNOS inhibition on spontaneous gallbladder motility. mRNA extracted from normal possum gallbladders was analysed by PCR. Gallbladder contractility was evaluated using a highly selective iNOS inhibitor AR-C102222AA (AR-C) in in vitro muscle strips (0.1-10 000 microm) and in vivo (0.1-30 micromol kg(-1)) experiments. Gene expression analysis revealed the presence of iNOS mRNA in normal gallbladder (n = 3). In vitro, AR-C (0.1-1000 micromol L(-1)) produced a concentration-dependent increase in spontaneous gallbladder contractile activity and basal tension (P < 0.05; n = 6). The maximum effect was a 1.8-fold increase in activity and 2.1-fold increase in basal tension. Pretreatment of muscle strips with tetrodotoxin (1 micromol L(-1)) did not block the AR-C-induced response (n = 5). In vivo, AR-C (30 micromol kg(-1), i.v.) increased gallbladder contraction frequency (P < 0.05; n = 8). These data suggest that iNOS is continually expressed in the normal gallbladder, which presumably releases low levels of nitric oxide and in turn may modulate spontaneous gallbladder motility. AR-C may be a beneficial treatment for patients suffering from acute cholecystitis.

Sphincter of Oddi function in the Australian brush-tailed possum is inhibited by intragastric ethanol.

The role of sphincter of Oddi (SO) function in alcoholic acute pancreatitis (AP) is unclear. We aimed to compare the effect of i.v. and intragastric (IG) ethanol on SO function (i.e. trans-sphincteric flow; TSF) and investigate possible neural mechanisms. The involvement of gastric mucosal damage was also investigated by pretreatment with pantoprazole. In anaesthetized Australian possums, blood pressure (BP), TSF and blood ethanol concentrations were measured after i.v. or IG ethanol. Possums were subjected to acute vagotomy, atropine, L-nitro arginine methyl ester (L-NAME) or pantoprazole pretreatment prior to IG ethanol. BP was not significantly altered by ethanol. Ethanol decreased TSF in a dose and route-dependent manner. The lowest dose of IG ethanol reduced TSF but this response was not duplicated by i.v. ethanol producing the same blood ethanol concentrations. Acute vagotomy, atropine or L-NAME pretreatment blocked the ethanol-induced decrease in TSF and simultaneously suppressed the blood ethanol concentration. Pantoprazole pretreatment reduced the TSF response and blood ethanol concentrations implicating mechanisms induced by gastric mucosal damage. We conclude that ethanol (and/or its metabolites) reduces TSF via humoral and neural mechanisms involving vagal pathways, muscarinic receptors and nitric oxide. Reduced TSF could contribute to the onset of AP.

Exogenous purines induce differential responses in the proximal and distal regions of the possum sphincter of Oddi.

1. The aim of this study was to compare the effect of exogenous ATP and adenosine on spontaneous motility of the proximal and distal regions of the possum sphincter of Oddi (SO). 2. ATP or adenosine (1 microm-1 mm) was applied to distal-SO or proximal-SO muscle rings in organ baths in the absence or presence of tetrodotoxin (TTX) or P1/P2 antagonists. 3. Both ATP and adenosine altered spontaneous activity, predominantly in proximal-SO rings. 4. Exogenous ATP induced a bi-phasic response consisting of a brief TTX-sensitive excitatory component, and a longer-lasting TTX-insensitive inhibitory component. 5. The excitatory ATP response likely involves P2X receptors, whereas the late inhibitory response likely involves P2Y receptors. 6. Exogenous adenosine decreased spontaneous SO activity, via a TTX-insensitive mechanism. 7. Exogenous purines modulate SO motility, acting primarily in the proximal region of the SO, via neural and non-neural mechanisms and multiple purine receptor subtypes.

Exogenous adenosine triphosphate and adenosine stimulate proximal sphincter of oddi motility via neural mechanisms in the anesthetized Australian possum.

We aimed to determine if exogenous adenosine triphosphate or adenosine modulated sphincter of Oddi motility and involved neural mechanisms. Sphincter of Oddi motility was recorded in anesthetized possums by manometry. Adenosine triphosphate or adenosine (1 microM-10 mM) was applied topically to the sphincter before and after pretreatment with tetrodotoxin, hexamethonium, atropine, or Nomega-nitro-L-arginine methyl ester. Sphincter contraction amplitude and frequency were quantified. Adenosine triphosphate induced a concentration-dependent increase in proximal sphincter contraction amplitude and frequency (P < 0.05). This response was reduced by tetrodotoxin and atropine but enhanced by hexamethonium and Nomega-nitro-L-arginine methyl ester. Adenosine concentration dependently increased proximal sphincter contraction amplitude (P < 0.05) only. This response was reduced by tetrodotoxin, atropine, and Nomega-nitro-L-arginine methyl ester, whereas hexamethonium had no effect. We conclude that exogenous adenosine triphosphate and adenosine stimulate proximal sphincter of Oddi motility via neural mechanisms, involving cholinergic motor neurons. Adenosine triphosphate may further modulate sphincter motility via nicotinic and nitrergic pathways.

Surgical versus endoscopic treatment of bile duct stones.

BACKGROUND: 10% to 18% of patients undergoing cholecystectomy for gallstones have common bile duct (CBD) stones. Treatment options for these stones include pre- or post-operative endoscopic retrograde cholangiopancreatography (ERCP) or open or laparoscopic surgery. OBJECTIVES: To systematically review the management of CBD stones by four approaches: (1) ERCP versus open surgical bile duct clearance. (2) Pre-operative ERCP versus laparoscopic bile duct clearance. (3) Post-operative ERCP versus laparoscopic bile duct clearance. (4) ERCP versus laparoscopic bile duct clearance in patients with previous cholecystectomy. SEARCH STRATEGY: We systematically searched key relevant electronic databases, bibliographies of relevant papers, and abstracts of relevant subspecialty meetings until November 2005. SELECTION CRITERIA: The quality of included trials was assessed by adequacy of allocation sequence generation, allocation concealment, blinding, and follow-up. DATA COLLECTION AND ANALYSIS: Published and unpublished data relevant to 12 predefined outcome measures were used to conduct fixed- and random-effects models meta-analyses, with exploration of heterogeneity and use of sensitivity and subgroup analysis where required. MAIN RESULTS: Thirteen trials randomised 1351 patients. Eight trials (n = 760) compared ERCP with open surgical clearance, three (n = 425) compared pre-operative ERCP with laparoscopic clearance, and two (n = 166) compared post-operative ERCP with laparoscopic clearance. There were no trials of ERCP versus laparoscopic clearance in patients without an intact gallbladder. Methodology was considered adequate in at least two of three assessable fields in ten trials. A significantly increased number of total procedures (including for complications) per patient was seen in the ERCP arms in all three comparisons with weighted mean differences of 0.62 (95% CI 0.15 to 1.09), 0.96 (95% CI 0.96 to 0.96), and 1.09 (95% CI 0.93 to 1.24), respectively. ERCP was less successful than open surgery in CBD stone clearance (Peto OR 2.89, 95% CI 1.81 to 4.61) with a tendency towards higher mortality (risk difference 1%, 95% CI -1% to 4%). Laparoscopic CBD stone clearance was as efficient as pre- (Peto OR 1.00, CI 0.53 to 1.80) and post-operative ERCP (OR 2.27, 95% CI 0.37 to 13.9) and with no significant difference in morbidity and mortality. Laparoscopic trials universally reported shorter hospital stays in surgical arms. Insufficient data were reported for cost analysis. AUTHORS' CONCLUSIONS: In the era of open cholecystectomy, open bile duct surgery was superior to ERCP in achieving CBD stone clearance. In the laparoscopic era, data are close to excluding a significant difference between laparoscopic and ERCP clearance of CBD stones. The use of ERCP necessitates increased number of procedures per patient.

Pancreatobiliary afferent recordings in the anaesthetised Australian possum.

The sensory innervation to the pancreatobiliary system is poorly characterized. Afferent signals from the gastrointestinal tract and biliary tree are transmitted to the central nervous system via the vagus and spinal nerves. We aimed to record afferent discharge in order to characterize the vagal and splanchnic afferent signals from the possum upper gastrointestinal tract, biliary tree and pancreas. In 21 anaesthetised possums nerve fibres were teased from the vagus or splanchnic nerve for multi-unit recording. Mechanical stimuli consisted of balloon distension of the gallbladder and duodenum (2-7 ml) and fluid distension (0-20 mm Hg) of the bile or pancreatic ducts. Approximately 60% of fibres from all nerves displayed spontaneous discharge. Spinal afferent responses to mechanical stimuli were infrequent (n=13). Increased discharge occurred in response to duodenal (12/99 fibres) or gallbladder (7/96 fibres) distension, but not to bile duct (0/73 fibres) or pancreatic duct (0/51 fibres) distension. Vagal afferent responses to distension of the duodenum or stomach (5-30 ml) were more common (n=8). Increased discharge was recorded in response to duodenal (49/134 fibres), or gastric (22/70 fibres) distension. Responses to gallbladder distension were less frequent (6/99 fibres) and as with the spinal afferent no response to bile duct (0/66) or pancreatic duct (0/70) distension were recorded. We conclude that mechanosensitive afferents in the pancreatobiliary system are relatively rare, particularly within the ducts, and/or that they are adapted to monitor stimuli other than luminal distension.

The sphincter of Oddi: understanding its control and function.

The most common functional disorders of the biliary tract and pancreas are associated with disordered motility of the sphincter of Oddi (SO). The SO is a neuromuscular structure located at the junction of the bile and pancreatic ducts with the duodenum. The primary functions of the SO are to regulate the delivery of bile and pancreatic juice into the duodenum, and to prevent the reflux of duodenal contents into the biliary and pancreatic systems. Disordered motility of the SO leads to the common and painful clinical conditions of SO dysfunction and acute pancreatitis. In order to understand normal SO motility, studies have been performed addressing SO function, control of spontaneous SO activity, responses to bioactive agents, SO innervation, and reflexes with other gastrointestinal organs. These studies have led to the current understanding of how the SO functions and may permit the development of targeted therapy for SO dysfunction and acute pancreatitis. This review summarizes the current knowledge regarding the control and regulation of SO motility, highlighting laboratory based and clinical research performed over the last 5 years.

Electrical activation of common bile duct nerves modulates sphincter of Oddi motility in the Australian possum.

BACKGROUND: Sphincter of Oddi (SO) motility is regulated by extrinsic and intrinsic nerves. The existence of neural circuits between the SO and the proximal extrahepatic biliary tree has been reported, but they are poorly understood. Using electrical field stimulation (EFS), we determined if a neural circuit exists between the common bile duct (CBD) and the SO in anaesthetized Australian brush-tailed possums. METHODS: The gallbladder, cystic duct or CBD were subjected to EFS with a stimulating electrode. Spontaneous SO phasic waves were measured by manometry. RESULTS: EFS at sites on the distal CBD (12-20 mm proximal to the SO), but less commonly at more proximal CBD, evoked a variety of responses consisting of an excitatory and/or inhibitory phase. Bi-phasic responses consisting of an excitation followed by inhibition were the most common. Tri-phasic responses were also observed as well as excitation or inhibition only. These evoked responses were blocked by topical application of local anaesthetic to the distal CBD or transection of the CBD. EFS at sites on the gallbladder body, neck or cystic duct did not consistently evoke an SO response. Pretreatment with atropine or guanethidine reduced the magnitude of the evoked response by about 50% (p<0.05), pretreatment with hexamethonium had no consistent effect and pretreatment with a nitric oxide synthase inhibitor increased the response. DISCUSSION: A neural circuit(s) between the SO and the distal CBD modulates SO motility. Damage to this area of the CBD during bile duct exploration surgery could adversely affect SO motility.

Scorpion venom stimulates biliary/duodenal motility and pancreatic exocrine secretion.

Scorpion envenomation causes severe upper abdominal pain associated with nausea and vomiting. Although scorpion venom (SV) stimulates pancreatic and gastric secretion in animal models, its effects on duodenal and biliary motility have not been reported. The aim of this study was to determine the effects of SV on sphincter of Oddi (SO), duodenal and gall bladder motility and pancreatic amylase output. Anaesthetized Australian possums (n = 21) were infused with SV via intravenous or closed intra-arterial routes. Blood pressure, SO, duodenal and gall bladder motility were continuously monitored for 4 h. Trans-sphincteric flow (TSF), an indicator of bile duct resistance, was measured concurrently. The amylase output in pancreatic juice was also measured. SV infusion resulted in profound transient increase in blood pressure, SO motility and a significant decrease in TSF. No significant differences were noted in SO basal pressure changes. A transient increase in gall bladder tone, duodenal contraction amplitude and frequency, and amylase output were noted. Following the peak in blood pressure, amylase output, SO, gall bladder and duodenal motility were depressed. SV induces a rapid but transient increase in biliary and duodenal motility that is associated with stimulation of pancreatic amylase output. These changes may contribute to gastrointestinal symptoms associated with early phases of envenomation.

Highly selective iNOS inhibition and sphincter of Oddi motility in the Australian possum.

AIM: Inducible nitric oxide synthase (iNOS) plays a major role in acute pancreatitis. Selective inhibitors of iNOS are being developed as therapeutic agents. Sphincter of Oddi (SO) dysfunction may cause pancreatitis and nitric oxide is necessary for SO relaxation. A new highly selective iNOS inhibitor, AR-C102222AA (AR-C), is evaluated together with the established iNOS inhibitor, L-N(6)-(1-iminoethyl)lysine (L-NIL), and the selective neuronal nitric oxide synthase (nNOS) blocker S-methyl-l-thiocitrulline (SMTC). METHODS: In anaesthetized Australian Brush-tailed possums, the effect of topical, i.v. or i.a. administration of these drugs was evaluated on spontaneous SO motility, blood pressure (BP) and pancreatic vascular perfusion. SO motility was recorded by manometry and pancreatic vascular perfusion by laser Doppler fluxmetry. Also, the effect of SMTC and AR-C on electrical field stimulation (EFS)-induced non-cholinergic non-adrenergic (NANC) SO relaxation in vitro was evaluated. RESULTS: Infusion of AR-C (0.1-30 micromol kg(-1)) increased SO contraction frequency (P = 0.026) only at the two highest doses. L-NIL infusion (0.15 to 14.7 micromol kg(-1)) also increased SO contraction frequency at 8.8 micromol kg(-1) (P < 0.05) and reduced SO contraction amplitude at the two highest doses (P < 0.05). SMTC injections (0.5 nmol-2.4 micromol) produced a dose-dependent increase in SO contraction frequency (P = 0.009), but no effect was seen on the other parameters. In vitro SMTC (40-400 microm) inhibited EFS-induced NANC relaxation in a dose-dependent manner (P < 0.0005). In contrast AR-C (10-500 microm) had no effect on EFS-induced NANC relaxation (P > 0.05). CONCLUSIONS: At low doses, AR-C does not effect SO motility or EFS-induced NO mediated relaxation. However, high doses of AR-C and L-NIL in vivo influenced SO motility by inhibiting nNOS activity and these effects need be considered in relation to therapeutic doses of this agent.

Endogenous endothelin increases gallbladder tone and leads to acute cholecystitis in the Australian possum.

Endothelins are bioactive peptides produced by gallbladder epithelial cells. We aimed to determine the role of endothelins in acute cholecystitis. Escherichia coli lipopolysaccharide vs saline (sham) was instilled into the gallbladder lumen of Australian possums. Some animals received the non-selective endothelin antagonist, tezosentan. At 4 or 24 h, plasma and gallbladder endothelins and white blood cell count (WBCC) were determined. Acute cholecystitis was assessed using a histopathology score. In other animals gallbladder tone was determined. At 4h, a dose-dependent 60-fold increase in gallbladder endothelin level occurred (P = 0.001) but other parameters remained comparable with sham animals. Epithelial cells were endothelin-immunoreactive. At 24 h, the WBCC rose (P < 0.007), and severe cholecystitis developed. Gallbladder but not plasma endothelin levels remained elevated. Tezosentan pre-treatment resulted in a histologically normal gallbladder, but the WBCC and gallbladder endothelin levels were elevated. Lipopolysaccharide or saline instillation also caused a time-dependent increase in gallbladder tone over 4 h (P < 0.001), but not in control animals. This increase was reduced by tezosentan treatment. Gallbladder endothelin production is an early event in acute cholecystitis, increases gallbladder tone and plays a crucial role in the inflammatory process.