The arginine/nitric oxide pathway modulates sphincter of Oddi motor activity in guinea pigs and rabbits

Comparative Relaxant Effects of Ataciguat and Zaprinast on Sheep Sphincter of Oddi

BACKGROUND

Relaxing the sphincter of Oddi (SO) is an important process during endoscopic retrograde cholangiopancreatography (ERCP) procedures. This issue suggests that the easier the sphincterotomy and cannulation, the more post-ERCP complications decrease.

AIMS

To compare the relaxant effects of ataciguat (a novel soluble guanylyl cyclase activator) and zaprinast (an inhibitor of phosphodiesterase 5) on sheep SO in vitro, thus testing whether they can be used during ERCP.

STUDY DESIGN

Animal experimentation.

METHODS

Sheep SO rings were placed in tissue baths and their isometric tension to ataciguat and zaprinast were tested. We also tested their isometric tension against ataciguat in the presence of 1H-(1,2,4) oxadiazole (4,3-a) quinoxalin-1-one (ODQ) which is a soluble guanylyl cyclase inhibitor.

RESULTS

Ataciguat and zaprinast both triggered concentration addicted relaxation on sheep SO rings (p=0.0018, p=0.0025 respectively) but the relaxation of the ataciguat was significantly greater than that of zaprinast at all concentrations (p=0.0024). It was observed that decreased relaxation responses were initiated by ataciguat in the presence of ODQ (p=0.0012).

CONCLUSION

Ataciguat and zaprinast both have relaxing effects on sphincter of Oddi, although that of zaprinast is lower. We believe that ataciguat and zaprinast can be used in ERCP procedures in order to relax the sphincter of Oddi and thus can be used locally in order to decrease complications.

Effects of hyperhomocysteinemia on non-adrenergic non-cholinergic relaxation in isolated rat duodenum

The effect of hyperhomocysteinemia induced by pretreatment with methionine 12 weeks prior to the study on the responses induced by gamma-aminobutyric acid (GABA), electrical field stimulation (EFS), and ATP have been evaluated in isolated rat duodenum. In the presence of adrenergic and cholinergic blockade, EFS (60 V, 1 ms, 1-3 Hz) induced frequency-dependent relaxations of the preparation. GABA and ATP also caused submaximal relaxation of the rat duodenum. The relaxations induced by GABA, EFS, and ATP were not significantly changed in duodenal tissues from hyperhomocysteinemic rats compared with control rats. GABA- and EFS-induced relaxations were inhibited by N-nitro-L-arginine methyl ester (L-NAME; 3 x 10(-4) M) in both hyperhomocysteinemic and control rats. On the other hand, L-NAME incubation did not affect ATP-induced relaxation. These results suggest that hyperhomocysteinemia does not cause an important impairment on non-adrenergic non-cholinergic innervation of the rat duodenum.

Comparative relaxant effects of YC-1 and DEA/NO on the sheep sphincter of Oddi

BACKGROUND/AIMS

Nitric oxide (NO) is a major inhibitor in various parts of the gastrointestinal tract. This study was designed to compare the effects of YC-1, NO-independent soluble guanylate cyclase (sGC) activator, and DEA/NO, NO-nucleophile adduct, on sheep sphincters of Oddi (SO).

METHODS

SO rings were mounted in a tissue bath and tested for changes in isometric tension in response to 3-(5'-hydroxymethyl-2'-furyl)-1-benzyl indazole (YC-1, 10(-10)-10(-5)M), diethylamine/NO complex (DEA/NO, 10(-8)-10(-4)M). We also evaluated the effect of YC-1 (10(-6) and 10(-5)M) and DEA/NO (10(-5) and 10(-4)M) on the levels cyclic GMP (cGMP) in isolated SO.

RESULTS

YC-1 (10(-10)-10(-5) M) and DEA/NO (10(-8)-10(-4)M) induced concentration-dependent relaxation of isolated SO rings precontracted with carbachol (10(-6)M). The pEC(50) value of DEA/NO was significantly lower than those for YC-1 (p < 0.05), with no change of E(max) values. YC-1 increased cGMP levels more than control, carbachol and DEA/NO groups (p < 0.05).

CONCLUSION

These results show that YC-1 is a more potent relaxant than DEA/NO and causes more elevation of cGMP levels in isolated SO rings.

Diagnosis of gallbladder dyskinesia by quantitative hepatobiliary scintigraphy

AIM

The aim of the present study was to develop a new pharmacologic method during hepatobiliary scintigraphy by which patients with functional and organic forms of gallbladder (GB) dysfunction can be differentiated.

METHODS

Quantitative hepatobiliary scintigraphy (QHBS) was performed on 31 patients with impaired GB motility selected by cerulein-augmented ultrasonography. Nineteen patients had acalculous biliary pain (ABP) and suspected GB dyskinesia, 6 patients had celiac disease, and 6 patients had type II diabetes mellitus. Sixty minutes after the isotope administration, 1 ng/bwkg/min cerulein (CCK10) was infused for 10 minutes, and then from the 90th minute, an equivalent dose of CCK10 was infused in the presence of 0.5 mg sublingual glyceryl trinitrate (GTN) in 12 or placebo in 7 consecutive patients. The GB ejection fraction (GBEF) was calculated repeatedly in time periods from 60 to 90 and from 90 to 120 minutes.

RESULTS

In the majority of patients with ABP and suspected GB dyskinesia, CCK10 and GTN coadministration normalized the previously impaired GB-emptying. When the cumulative results of all 12 patients were calculated, we demonstrated significant differences (P=0.003) in the GBEF between the first (CCK10) versus the second (CCK10 plus GTN) stimuli: 19+/-11% versus 40+/-17%, respectively. In contrast, in 12 patients with celiac sprue and diabetes mellitus, no differences in the GBEF were detected when the first (CCK10 alone) versus the second (CCK10 plus GTN) stimuli was compared: 21+/-10% versus 22+/-13%, respectively. Finally, placebo and CCK10 coadministration in 7 consecutive patients with ABP and suspected GB dyskinesia did not influence the GBEF as compared with CCK10 alone: 13+/-9% versus 15+/-10%, respectively.

CONCLUSION

GTN and CCK10 coadministration induces a significant improvement of the GBEF in patients with GB dyskinesia. The application of this new pharmacologic test during QHBS permitted the noninvasive separation of those patients with secondary impaired GB-emptying as a result of GB dyskinesia from those with primary forms of GB hypokinesia.

Gastrointestinal Function Regulation by Nitrergic Efferent Nerves

Gastrointestinal (GI) smooth muscle responses to stimulation of the nonadrenergic noncholinergic inhibitory nerves have been suggested to be mediated by polypeptides, ATP, or another unidentified neurotransmitter. The discovery of nitric-oxide (NO) synthase inhibitors greatly contributed to our understanding of mechanisms involved in these responses, leading to the novel hypothesis that NO, an inorganic, gaseous molecule, acts as an inhibitory neurotransmitter. The nerves whose transmitter function depends on the NO release are called "nitrergic", and such nerves are recognized to play major roles in the control of smooth muscle tone and motility and of fluid secretion in the GI tract. Endothelium-derived relaxing factor, discovered by Furchgott and Zawadzki, has been identified to be NO that is biosynthesized from l-arginine by the constitutive NO synthase in endothelial cells and neurons. NO as a mediator or transmitter activates soluble guanylyl cyclase and produces cyclic GMP in smooth muscle cells, resulting in relaxation of the vasculature. On the other hand, NO-induced GI smooth muscle relaxation is mediated, not only by cyclic GMP directly or indirectly via hyperpolarization, but also by cyclic GMP-independent mechanisms. Numerous cotransmitters and cross talk of autonomic efferent nerves make the neural control of GI functions complicated. However, the findingsrelated to the nitrergic innervation may provide us a new way of understanding GI tract physiology and pathophysiology and might result in the development of new therapies of GI diseases. This review article covers the discovery of nitrergic nerves, their functional roles, and pathological implications in the GI tract.

Investigation of the mechanism of nicotine-induced relaxation on the sheep sphincter of Oddi

Possible mechanisms for nicotine-induced relaxation were investigated in the isolated sheep's sphincter of Oddi. Sheep's sphincter of Oddi rings were mounted in tissue bath with modified Krebs-Henseleit solution and aerated with 95% oxygen and 5% carbon dioxide. Tension was measured with isometric force transducers, and muscle relaxation was expressed as percent decrease of precontraction induced by carbachol. Nicotine (1 x 10(-5) to 3 x 10(-3) mol/L) produced concentration-dependent relaxation on sphincter of Oddi precontracted by carbachol (10(-6) mol/L). Nicotine-induced relaxation was 72.8 +/- 4.2% of precontraction with carbachol (10(-6) mol/L) (mean pD2 value, 3.76 +/- 0.05 mol/L). Nicotine-induced relaxation was not affected by N(w)-nitro L-arginine methyl ester (L-NAME) (3 x 10(-5) mol/L), methylene blue (10(-5) mol/L), indomethacin (10(-5) mol/L), hexamethonium (10(-5) mol/L), glibenclamide (10(-5) mol/L), 4-aminopyridine (10(-3) mol/L), tetraethylammonium (3 x 10(-4) mol/L), clotrimazole (10(-6) mol/L), 5-nitro-2-(3-phenylpropylamino) benzoic acid (NPPB) (10(-6) mol/L), and anthracene-9-carboxylate (9-AC) (10(-6) mol/L), but potentiated by bupivacain (10(-5) mol/L). A calcium-antagonizing effect of nicotine was not observed. The results suggest that nicotine-induced relaxation of the sheep's sphincter of Oddi is not mediated by the release of prostaglandins, nitric oxide (NO), or a related substance; by the activation of potassium channels or chloride channels; or by the stimulation of nicotinic cholinoceptors. Potentiation of the nicotine-induced relaxation by bupivacain indicates that blockade of sodium channels may play a role in this relaxation.

Does topical GTN on the sphincter of Oddi facilitate ERCP? A double-blind randomized control trial

BACKGROUND

Endoscopic retrograde cholangio pancreatography (ERCP) is a technically challenging procedure. Glyceryl trinitrate (GTN) has been shown to reduce tone in the sphincter of Oddi (SO), cannulation of which is a rate-limiting factor. A double-blind randomized control trial was performed to assess whether topical GTN on the SO would facilitate cholangiography and/or bile duct cannulation.

METHODS

104 patients requiring ERCP for biliary symptoms were randomized into two groups, 52 controls pretreated with 5 ml 0.9% normal saline (NS) and 52 pretreated with 5 ml GTN (concentration 1 mg/ml).

RESULTS

There was no significant between the control group and the GTN group in primary cannulation rate (p = 0.76), time taken to cholangiography (p = 0.58), or time to cannulation (p = 0.43).

CONCLUSION

Topically administered GTN to the SO does not aid in obtaining a cholangiogram or cannulation during an ERCP.

Treatment of chronic anal fissure by application of L-arginine gel: a phase II study in 15 patients

PURPOSE

Local application of exogenous nitric oxide donors, such as isosorbide dinitrate and glyceryl trinitrate, promotes fissure healing by reducing anal resting pressure and improving anodermal blood flow. The major drawback of these nitric oxide donors is headache. The overall incidence of this side effect is approximately 40 percent. Recently we have shown in healthy volunteers that L-arginine, being an intrinsic precursor of nitric oxide, reduces anal resting pressure without headache as a side effect. The aim of the present study was to evaluate the effect of L-arginine on anal resting pressure, anodermal blood flow, and fissure healing in patients with chronic anal fissure.

METHODS

Fifteen patients with a chronic anal fissure were included in the present study. Before entering the study 10 patients were unsuccessfully treated by local application of isosorbide dinitrate. Six of these patients experienced severe headache during treatment with isosorbide dinitrate. All patients were treated for at least 12 weeks by local application of a gel containing L-arginine 400 mg/ml five times a day. In patients with a persistent fissure, treatment was continued until 18 weeks. Anal manometry and laser Doppler flowmetry of the anoderm were performed before treatment, 20 minutes after local application of the first dose, and after 12 weeks of treatment. A visual analog scale was used to assess fissure-related pain and headache.

RESULTS

One patient dropped out after one day of treatment, and one was excluded because of violation of the study protocol. After 12 weeks of treatment complete fissure healing was observed in 3 of 13 (23 percent) patients, and after 18 weeks the healing rate was 8 of 13 (62 percent) patients. None of the 13 patients experienced typical nitric oxide-induced headache. The pressure recordings showed a significant reduction of maximum anal resting pressure (mean +/- SD): pretreatment 89 +/- 17 mmHg; 20 minutes after application of the first dose 67 +/- 17 mmHg; 12 weeks after treatment 74 +/- 14 mmHg (P < 0.005). Recordings of anodermal blood flow showed a significant increase in flow: pretreatment 0.36 +/- 0.25 volts; 20 minutes after application of the first dose 0.59 +/- 0.27; 12 weeks after treatment 0.64 +/- 0.33 (P < 0.005).

CONCLUSIONS

Local application of L-arginine promotes fissure healing without headache as a side effect, and L-arginine is effective even in patients not responding to isosorbide dinitrate treatment.

Effects of Nitric Oxide Synthase Inhibitor on the Digestive System Measured by Simultaneous Monitoring of Gastric Motility, Gastric Emptying Activity and Postprandial Pancreaticobiliary Secretion in Dogs

Relationships between the NO synthase inhibitor and gastric and pancreaticobiliary functions measured simultaneously in the digestive state have been little studied. The aim of this study was to estimate the effect of NO synthase inhibitor on integrated digestive function in conscious dogs. A strain gauge force transducer was implanted on the gastric antrum of 6 mongrel dogs to measure gastric contractile activity and two duodenal cannulas were inserted into the proximal and distal sites to measure the gastric emptying rate and the pancreaticobiliary output into the duodenum using our novel method. Postprandial pancreatic and biliary secretion were presented as amylase and bile acid activity, respectively. Furthermore, a cervical cannula was placed into the superior vena cava as a route for the administration of NO synthase inhibitor, N omega-nitro-L-arginine (L-NNA), at a dose of 2.5 mg/kg-h. In a group given L-NNA, gastric contractile activity after ingestion was significantly enhanced, but the emptying rates of gastric solids and liquids were significantly suppressed in comparison with the control. The mean 0-1 h amylase integrated output was significantly (P < 0.05) decreased in comparison with the control, and the mean bile acid integration of 0-1 h output was also significantly (P < 0.01) decreased. A possible explanation for this observation is that smaller volumes of nutrient are delivered into the duodenum; however, it could also be that postprandial pancreaticobiliary secretion is inhibited by an alteration of blood flow or by a change in contractions of the sphincter of Oddi after the administration of L-NNA.

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.

Chinese medicinal herbs Muh-Shiang Bin-Lang-Wan increases the motility of sphincter of Oddi in anesthetized rabbits through activation of M1 muscarinic receptors

The sphincter of Oddi (SO) plays an important role in regulating the bile flow into the duodenum. This study was designed to investigate the effect of Chinese Medicinal Herbs Muh-Shiang-Bin-Lang-Wan (MSBLW) and their mechanism of action on regulating the motility of SO in rabbits. The activity of SO in anesthetized rabbits was measured by using a continuously perfused open-tip manometric method. The rabbits were administered with different doses of MSBLW through naso-gastric tubes. The SO motility before and after the administration of MSBLW were recorded, and analyzed with a computer equipped with an off line analysis software. The results showed that the SO activity, in terms of tonic pressure and phasic contraction pressure, were significantly changed. A significant lower tonic pressure and a higher phasic contraction pressure were noticed 40-60 min after administration of MSBLW with a peak response at 0.5-1.0 gm range. The responses were blocked by pretreatment of muscarinic receptors (M1) antagonist, pirenzepine (10 mg/kg, orally). We conclude that MSBLW is effective in increasing the SO motility in rabbits through activation of M1 muscarinic receptors. However, potential application of MSBLW in the treatment of human biliary disorders needs further evaluation.

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The effect of transcutaneous nerve stimulation on intraductal biliary pressure in post-cholecystectomy patients with T-drainage

OBJECTIVE

To evaluate the effects of transcutaneous electrical nerve stimulation (TENS) on intraductal biliary pressure (IDP) in basal conditions and after intravenous morphine and oral meal stimulation.

DESIGN AND METHODS

Fifteen patients (5 male, 10 female) aged 31-83 years (mean 61.5 +/- 13.7 years) with prior cholecystectomy and residual in situ T-tube were examined. Final radiographs excluded any organic abnormalities. The study consisted of three sessions. On the first day (session 1), after the initial manometric intraductal pressure was measured for 15 min, TENS (using a PRO-TENS pocket stimulator) was applied for 15 min. Measurement was continued for 15 min after termination of TENS. The measurement was performed using a water-perfused manometry system (Synectics Medical, Stockholm, Sweden) by a triple-channel manometric catheter inserted into the common bile duct through a T-drain. On the following day (session 2), the protocol was similar except that, after basal IDP measurement, morphine hydrochloride 0.08 mg/kg was injected intravenously 10 min before TENS. On the third day (session 3), after basal measurements were taken, patients were given a standard test meal and the IDP was recorded continuously for 45 min. To estimate the effects of the stimuli applied, absolute intraductal pressure changes were analysed.

RESULTS

In session 1, TENS reduced basal IDP in all patients by a mean of 3.95 +/- 1.6 mmHg. In 13 patients, 15 min after cessation of TENS a further decrease in IDP was observed. In two patients, termination of TENS was followed by a rebound increase in IDP; however, it did not reach the initial value (mean total decrease 5.05 +/- 2.25 mmHg). In session 2, administration of morphine produced an evident increase in IDP in all subjects by 6.9 +/- 2.7 mmHg. TENS decreased IDP in 13 patients. In two patients, TENS initially failed to lower elevated pressure, but it appeared several minutes after the end of stimulation. In 13 patients, the final IDP values were lower than the baseline pressures. In session 3, after administration of a test meal, IDP decreased within 30-40 min by a mean of 4.89 +/- 1.29 mmHg.

CONCLUSIONS

TENS decreased basal as well as elevated IDP in the majority of the T-drain patients studied. The effect of TENS persisted after its termination. Elevated IDP is believed to be responsible for pain in patients with sphincter of Oddi dysfunction (SOD). Therefore, we think that TENS can be used effectively and safely as an optional therapeutic method in the treatment of biliary dyskinesia.

Modulation of Cl-/OH- exchange activity in Caco-2 cells by nitric oxide

The present studies were undertaken to determine the direct effects of nitric oxide (NO) released from an exogenous donor, S-nitroso-N-acetyl pencillamine (SNAP) on Cl-/OH- exchange activity in human Caco-2 cells. Our results demonstrate that NO inhibits Cl-/OH- exchange activity in Caco-2 cells via cGMP-dependent protein kinases G (PKG) and C (PKC) signal-transduction pathways. Our data in support of this conclusion can be outlined as follows: 1) incubation of Caco-2 cells with SNAP (500 microM) for 30 min resulted in approximately 50% inhibition of DIDS-sensitive 36Cl uptake; 2) soluble guanylate cyclase inhibitors Ly-83583 and (1,2,4)oxadiazolo(4,3-a)quinoxalin-1-one significantly blocked the inhibition of Cl-/OH- exchange activity by SNAP; 3) addition of 8-bromo-cGMP (8-BrcGMP) mimicked the effects of SNAP; 4) specific PKG inhibitor KT-5823 significantly inhibited the decrease in Cl-/OH- exchange activity in response to either SNAP or 8-BrcGMP; 5) Cl-/OH-exchange activity in Caco-2 cells in response to SNAP was not altered in the presence of protein kinase A (PKA) inhibitor (Rp-cAMPS), demonstrating that the PKA pathway was not involved; 6) the effect of NO on Cl-/OH- exchange activity was mediated by PKC, because each of the two PKC inhibitors chelerythrine chloride and calphostin C blocked the SNAP-mediated inhibition of Cl-/OH- exchange activity; 7) SO/OH- exchange in Caco-2 cells was unaffected by SNAP. Our results suggest that NO-induced inhibition of Cl-/OH- exchange may play an important role in the pathophysiology of diarrhea associated with inflammatory bowel diseases.

Lipopolysaccharide temporarily impairs sphincter of Oddi motility

The aim of our study was to determine the effect of lipopolysaccharide (LPS) on sphincter of Oddi (SO) motility. Opossums received saline, Escherichia coli LPS (1.0 mg/kg), or E. coli LPS (1.0 mg/kg) and aminoguanidine (50 mg/kg), and the SO was removed 6-24 h later. At 12 h LPS decreased electrical field stimulation (EFS)-induced relaxation and increased baseline tone. These changes were reversed when the animals were pretreated with aminoguanidine. The dose-dependent decrease in EFS-induced relaxation by N(omega)-nitro-l-arginine was impaired after LPS, but not in animals that received LPS and aminoguanidine. The impaired EFS-induced relaxation after LPS was reversed when l-arginine was added to the tissue bath. Serum levels of NO(-)(2)/NO(-)(3) were increased with LPS as compared to saline or both LPS and aminoguanidine. Inducible nitric oxide synthase mRNA was readily seen in SO segments after LPS. LPS impairs EFS-induced relaxation and increases baseline tone of the SO. The effects of LPS on SO motility appear to be mediated by nitric oxide.

Nitric oxide formation in the dog sphincter of Oddi from nitric oxide donors as measured with in vivo micro-dialysis

BACKGROUND

Nitric oxide (NO) is known to play an important role in neurally mediated relaxation of the sphincter of Oddi.

AIM

We investigated whether NO donors, such as nitroglycerin or zwitterionic polyamine/NO, applied into the common bile duct or intravenously, may induce the relaxation of the sphincter of Oddi by producing NO in the anaesthetized dog.

METHODS

NO production in the sphincter of Oddi was measured by detecting NO oxidation products (NO2- and NO3-) using micro-dialysis methods.

RESULTS

Zwitterionic polyamine/NO and nitroglycerin applied into the common bile duct induced a marked increase in NO2- but not NO3-, in the sphincter of Oddi. Intravenous infusion of zwitterionic polyamine/NO and nitroglycerin induced little or no increase in NO2- formation. Nitroglycerin infused into either the common bile duct or intravenously administered produced relaxation of the sphincter of Oddi, but zwitterionic polyamine/NO had no effect on the sphincter of Oddi in spite of the increase in NO2- levels.

CONCLUSIONS

Locally or systemically applied NO donors induce relaxation of the sphincter of Oddi by producing NO, although their mode of action differs in different analogues.

A phase I study of oxidized raffinose cross-linked human hemoglobin

OBJECTIVE

To evaluate the safety of oxidized-raffinose cross-linked human hemoglobin, Hemolink, in normal healthy volunteers.

DESIGN

Randomized, placebo-controlled, double-blind study.

SETTING

Clinical research facility of a contract research organization.

PATIENTS

Forty-two healthy adult male volunteers of which 33 received Hemolink.

INTERVENTIONS

Oxidized-raffinose cross-linked and polymerized hemoglobin as a 10% (w/v) solution, in doses of 0.025-0.6 g/kg or an equivalent volume of lactated Ringer's solution, was infused intravenously on day 1, and subjects were monitored for 3 days in the clinical facility with < or =6 wks follow-up. Major organ function was assessed pre- and postinfusion, by hemodynamic, electrocardiographic, pulmonary function, and clinical chemistry measurements.

MEASUREMENTS AND MAIN RESULTS

Doses of 1.7-42 g of hemoglobin were administered with no serious adverse events noted. Abdominal pain of moderate to severe intensity was seen in some subjects at doses >0.4 g/kg and was alleviated with smooth muscle relaxants. There was a dose-dependent increase in mean arterial pressure with a plateau of approximately 14% above baseline at 0.1 g/kg. There was a concomitant reduction in heart rate, with no electrocardiographic abnormalities found. Respiratory function was not affected. There was a dose-dependent increase in serum bilirubin with values above the upper limit of normal at doses of > or =0.4 g/kg. Small increases in aspartate aminotransferase and alanine aminotransferase were noted in some patients, whereas alkaline phosphatase and gamma-glutamyltransferase remained in the normal range. Serum amylase concentrations were normal in 31 of 33 patients receiving Hemolink, whereas lipase was within the normal range in 21 of 33 patients. LDH was increased in a dose-dependent fashion. Two patients had increased creatine kinase concentrations, with a normal creatine kinase-MB mass fraction. All hematologic variables were within the normal range. The half-life of the oligomeric (>64 kDa) fraction of Hemolink was 18-20 hrs.

CONCLUSION

Oxidized-raffinose cross-linked hemoglobin, Hemolink, at doses < or =0.6 g/kg were well tolerated in healthy volunteers with no evidence of organ dysfunction. Further investigation of its potential use in surgical and trauma settings appears warranted.

Functional innervation of the biliary sphincter of the guinea-pig revealed by anti-autonomic drugs

1. The roles of excitatory and inhibitory intrinsic motor nerves on contractions reflexly evoked by wall distension were investigated in the isolated sphincter of Oddi of the guinea-pig (SO-GP). 2. Distension of the terminal bile duct for 30-60 s time periods increased the frequency of contractions from about 2 to 12 min(-1) (n = 16). 3. Hexamethonium (HEX; 300 microM) largely prevented the distension-evoked increase in contraction frequency (4.5 min(-1), n = 8) as did atropine (ATR; 1 microM) (0.8 min(-1), n = 6), while tetrodotoxin (TTX; 1 microM) blocked the contractions triggered during distension. 4. L-nitroarginine (L-NA; 100 microM) significantly increased the frequency of contractions during and in the absence distension while apamin (APAM; 0.5 microM) significantly increased their frequency and doubled their mean amplitude during distension. 5. These results suggest that distension activates excitatory cholinergic motor nerves to increase the frequency of contractions in the SO-GP. These actions are modulated by the concomitant activation of intrinsic nitrergic and non-nitrergic inhibitory motor nerves.

Endogenous nitric oxide mediates pancreatic exocrine secretion stimulated by secretin and cholecystokinin in rats

Nitric oxide (NO) is one of the important biologic mediators in regulation of gastrointestinal (GI) functions, but the influence of NO on the release of secretin and cholecystokinin (CCK) and exocrine pancreatic secretion has not been adequately investigated in the rat. The aim of this study was to determine the role of NO on endogenous and exogenous secretin- or CCK-stimulated pancreatic exocrine secretion both in anesthetized and conscious rats. Experiments were carried out in four different groups of rats with duodenal pancreatobiliary cannulas and jugular vein catheters. Group 1: During duodenal infusion of 0.05N HCl or 15% casein (pH 7.0), N-nitro-L-arginine (NNA), an inhibitor of NO-synthase in graded doses (2.5, 5, 10 mg/kg/h), was infused intravenously. Group 2: One hour after starting intravenous secretin at 5 pmol/kg/h or intravenous CCK-8 at 0.06 microg/kg/h, NNA in graded doses was administered intravenously. Group 3: In conscious rats, NNA (5 mg/kg/h) was given intravenously for 1 hour after a meal. Group 4: L-Arginine at 100 mg/kg/h was infused intravenously during the period of NNA (5 mg/kg/h) infusion in groups 1, 2, and 3. Pancreatic juice was collected at 30-minute intervals to measure volume, as well as output of bicarbonate and protein. At the end of the experiment, plasma secretin, vasoactive intestinal polypeptide (VIP) and CCK levels were determined by radioimmunoassay (RIA). NNA dose dependently inhibited the pancreatic secretion of fluid and bicarbonate stimulated by duodenal acidification, exogenous secretin, and a meal. NNA dose dependently inhibited the pancreatic secretion of protein stimulated by duodenal infusion of casein, exogenous CCK, and a meal. L-Arginine significantly reversed the NNA-induced inhibition of pancreatic secretion in all experiments. NNA did not alter significantly the plasma levels of secretin, VIP, and CCK. Our results indicated that endogenous NO plays a significant role in the regulation of pancreatic exocrine secretion stimulated by secretin and CCK. However, NO does not influence the release of secretin, VIP, or CCK in the rat.

Local somatothermal stimulation inhibits motility of the internal anal sphincter through nitrergic neural release of nitric oxide

PURPOSE

A somatoanal reflex had been demonstrated in our previous work. Because nitric oxide plays an important role in mediating relaxation of the internal anal sphincter, our purpose was to examine whether and how local somatothermal stimulation inhibits the function of the internal anal sphincter by stimulating nitric oxide release via nitrergic neurons and to elucidate the possible mechanism.

METHODS

The activity of the internal anal sphincter in anesthetized rabbits was measured by use of continuously perfused, open-tip manometric methods. Local somatothermal stimulation was achieved by applying an electroheating rod 1 cm away from the skin area at the right popliteal region. The responses were further manipulated by pre-treating the rabbits with agonists or antagonists linked to nitric oxide synthesis.

RESULTS

The motility of the internal anal sphincter before and during local somatothermal stimulation was significantly different (tonic pressure (mean +/-standard error of the mean), 5.4 +/- 0.3 vs. 4.9 +/- 0.3 mmHg, P = 0.0195; phasic pressure, 3.9 +/- 0.6 vs. 2.9 +/- 0.4 mmHg, P = 0.0002; frequency distribution of the phasic contractions (peak-to-peak interval), 28.9 +/- 3.7 vs. 65.3 +/- 10.4 seconds, P = 0.0001). The response began at approximately one minute after local somatothermal stimulation when the skin temperature was 41 +/- 0.3 degrees C. No anal response was observed when local somatothermal stimulation was applied at the control area. The local somatothermal stimulation-induced internal anal sphincter relaxation was not inhibited by pretreatment with atropine, propranolol, or phentolamine (tonic pressure, 5.8 +/- 1 vs. 5.2 +/- 0.8 mmHg, P = 0.038; phasic pressure, 4.2 +/- 0.9 vs. 3.1 +/- 0.6 mmHg, P = 0.020; peak-to-peak interval, 27.2 +/- 4.3 vs. 52.9 +/- 14.5 seconds, P = 0.043) but was completely blocked by pretreatment with a nitric oxide synthesis inhibitor. The effect of the nitric oxide synthesis inhibitor could be reversed by pretreatment with L-arginine (tonic pressure, 6 +/- 0.7 vs. 5.6 +/- 0.7 mmHg, P = 0.047; phasic pressure, 4.7 +/- 0.7 vs. 3.9 +/- 0.5 mmHg, P = 0.048; peak-to-peak interval, 23.8 +/- 3 vs. 33 +/- 3.7 seconds, P = 0.048), but not by D-arginine.

CONCLUSION

Local somatothermal stimulation inhibits internal anal sphincter motility through the activation of nonadrenergic noncholinergic neural release of nitric oxide. This procedure may represent a simplified approach for the treatment of anorectal diseases with hypofunction of the L-arginine/nitric oxide pathway. [Key words: Local somatothermal stimulation; Nitric oxide; Internal anal sphincter; Motility; Moxibustion] Jiang J-K, Chiu J-H, Lin J-K. Local somatothermal stimulation inhibits motility of the internal anal sphincter through nitrergic neural release of nitric oxide.

The effect of peroxynitrite on sphincter of Oddi motility

BACKGROUND

Nitric oxide (NO*) is an inhibitory neurotransmitter that induces sphincter of Oddi relaxation. Superoxide (O*-2)-scavenging enzymes are present in enteric plexuses of the sphincter of Oddi and O*-2 alters sphincter of Oddi motor function. O*-2 rapidly oxidizes nitric oxide (NO*) to form peroxynitrite (ONOO-), thus terminating the biological activity of NO*. The aim of our study was to determine the effects of ONOO- on sphincter of Oddi motility in vitro.

MATERIALS AND METHODS

Adult opossums were sacrificed and the sphincter of Oddi was removed and placed in a tissue bath containing oxygenated Krebs solution at 37 degreesC. In the first series of experiments, force transducers recorded tension in a transverse orientation at two sites along the spontaneously contracting sphincter of Oddi. In a second series of experiments, circular muscle strips were precontracted with carbachol and stimulated by an electrical field.

RESULTS

ONOO-, superoxide dismutase (SOD), Nomega-nitro-l-arginine (l-NNA), or oxyhemoglobin were added to the tissue baths. ONOO- decreased the frequency of contractions in the spontaneously contracting sphincter of Oddi. Adding hemoglobin increased the frequency of contractions. ONOO- also increased the stimulation-induced relaxation compared to controls. The increase in relaxation induced by ONOO- was inhibited by oxyhemoglobin and l-NNA but not SOD. Pretreatment with oxyhemoglobin prevented the increase in the stimulation-induced relaxation caused by ONOO-.

CONCLUSION

These results suggest that hemoglobin binds ONOO- or that ONOO- generates NO.

Local somatothermal stimulation inhibits the motility of sphincter of Oddi in cats, rabbits and humans through nitrergic neural release of nitric oxide

To examine whether and how local somatothermal stimulation inhibits the function of the sphincter of Oddi (SO) in humans and in animals with different types of SO, we measured the activity of SO in anesthetized cats and rabbits by using continuously perfused open-tip manometric methods. Local somatothermal stimulation was achieved by applying an electroheating rod 0.5 cm away from the skin area near the right subcostal region. A heating pad was applied to the corresponding area in patients undergoing endoscopic retrograde cholangiopancreatography and biliary manometry. The motility of the biliary tract in cats, in terms of gall bladder pressure, tonic and phasic contraction pressure and frequency of SO before and during local heat were significantly different, respectively. The local heat-induced SO relaxation was not inhibited by pretreatment with atropine, propranolol, phentolamine or anti-cholecystokinin-octapeptide, but was almost completely blocked by infiltration of local anesthetics. Pretreatment with a nitric oxide synthesis inhibitor also blocked the relaxation, which was reversed by pretreatment with L-arginine, but not by D-arginine. The inhibition of SO motility by local heat in rabbits was also blocked by pretreatment with L-NAME, and this blockade was reversed by L-arginine. Application of local heat on patients demonstrated obvious inhibitory SO responses. We conclude that local somatothermal stimulation inhibits the SO motility in animals with different types of SO through the activation of heat-sensitive neural release of nitric oxide. This procedure may represent a simplified approach for the treatment of diseases with hypofunction of the L-arginine/NO pathway.

Evidence supporting a role for ATP as non-adrenergic non-cholinergic inhibitory transmitter in the porcine ileum

The aim of this study was to investigate the nature of the non-adrenergic non-cholinergic (NANC) inhibitory transmitter of the circular muscle of the porcine ileum. For this purpose, the effects of putative NANC mediators i.e. NO, vasoactive intestinal polypeptide (VIP) and ATP were measured in isolated organ bath experiments (in basal conditions and after incubation with neostigmine 3 x 10[-5] M) and using the microelectrode technique. The NO donor sodium nitroprusside (NaNP) up to 10(-4) M, VIP up to 10(-7) M and ATP up to 10(-4) M failed to cause significant relaxation in the basal state. However, all of them induced marked relaxations when the tissue had been preincubated with neostigmine (3 x 10[-5] M) which was added to increase basal mechanical activity. The resting membrane potential (RMP) was unaffected by NaNP(up to 10(-4) M and VIP up to 10(-7) M whereas ATP (up to 10[-4] M) induced a transient hyperpolarization. The inhibitory junction potentials (IJPs) induced by electrical field stimulation (EFS) were not affected by N omega-nitro-L-arginine (L-NNA) (10[-4] M) whereas suramin, a purinoceptor antagonist, decreased (10[-4] M) or abolished (10[-3] M) the IJPs. Relaxations induced by ATP in neostigmine preincubated tissue were resistant to 10(-6) M tetrodotoxin, an axonal blocker, and inhibited by suramin. Apamin (10[-6] M, a small conductance calcium activated potassium channel blocker, completely abolished the IJP (n=5) and significantly decreased the relaxation induced by ATP (n=5). The present data provide support to the hypothesis that ATP is the NANC inhibitory transmitter in the porcine ileum acting on P2 muscular receptors. Nevertheless, VIP and NaNP do also cause relaxation of preparations preincubated with neostigmine.

Nitric oxide and the digestive system in mammals and non-mammalian vertebrates

The focus of the presentation will review the distribution of nitric oxide (NO)-producing sites in the digestive system in mammals and nonmammalian vertebrates and will center on the roles that NO plays in modulating physiological and pathophysiological functions in digestive system.

Duodenal but not gastric transection disturbs motility of the sphincter of Oddi in the dog

The aim of the present study was to elucidate the effect of gastric and duodenal transection on biliary manometry in anesthetized dogs. The basal biliary pressure and increase in pressure during saline perfusion at rates of 1.0 and 1.5 ml/min were studied in intact controls, during infusion of cholecystokinin (CCK) alone, and after gastric and duodenal transection. CCK dose-dependently lowered the basal pressure and the increase in pressure during perfusion. Gastric transection 1.5 cm proximal to the pylorus did not affect these parameters. In contrast, duodenal transection 1.0 cm distal to the pylorus significantly increased these parameters compared to all other groups. These observations suggest that the proximal duodenal transection, as performed during conventional distal gastrectomy, may contribute to the pathogenesis of postgastrectomy gallstone formation by altering motor function of the sphincter of Oddi.

Effects of recombinant human hemoglobin on opossum sphincter of Oddi motor function in vivo and in vitro

Nitric oxide (NO) acts as a nonadrenergic, noncholinergic inhibitor neurotransmitter that regulates sphincter of Oddi (SO) motor function. Hemoglobin blocks NO activity by binding it after it is synthesized. We hypothesized that recombinant human hemoglobin (rHb1.1) affects SO motor function by scavenging NO. Under anesthesia, 12 opossums underwent biliary tract manometry. Following a stabilization period, six animals were given rHb1.1 (0.28 g/kg over 30 min), while six received bovine albumin (0.28 g/kg over 30 min). Recordings were made during the infusion and for 3 hr after the infusion. In an in vitro preparation, force transducers were used to record spontaneous contractions at two sites along the sphincter segment. After a control period, rHb1.1 (0.1 mM) or cyanomethemoglobin (0.1 mM) was added to the tissue bath and recordings continued for another 2 hr. Recombinant human hemoglobin decreased the frequency of contractions, increased resting tone, and blocked the relaxation phase of contraction in vivo. It increased the baseline amplitude, the frequency, and the peak amplitudes of contractions in vitro. Albumin or cyanomethoglobin, which are unable to bind NO, had little effect on SO motor activity. We conclude that rHb1.1 may alter SO motor function by binding endogenous NO.

Functional role and histological demonstration of nitric-oxide-mediated inhibitory nerves in dog sphincter of Oddi

Nitric oxide (NO) plays an important physiological role in regulating gastrointestinal motility. Involvement of endogenous NO was evaluated in the response to non-adrenergic, non-cholinergic (NANC) nerve stimulation of the dog sphincter muscle of Oddi. Transmural electrical stimulation (TES), nicotine (10(-5) M) and K+ (10 mM) produced only a relaxation in the sphincter muscle strips contracted with substance P, which was not potentiated by atropine. The TES-induced relaxation was abolished by tetrodotoxin (3 x 10(-7) M) and oxyhaemoglobin (1.6 x 10(-5) M), but not affected by atropine (10(-7) M), propranolol (10(-7) M), phentolamine (10(-7) M), indomethacin (10(-6) M), cholecystokinin (CCK, 10(-8) M) and vasoactive intestinal polypeptide (VIP, 10(-8) M). The relaxation was also abolished by treatment with NG-nitro-L-arginine (L-NA, 10(-5) M), an NO synthase inhibitor. Nicotine produced a transient relaxation, which was abolished by tetrodotoxin, hexamethonium (10(-5) M) and L-NA, but not affected by atropine and NG-nitro-D-arginine (D-NA, 10(-5) M). The addition of K+ elicited a transient relaxation, which was abolished by tetrodotoxin and L-NA. The inhibitory effects of L-NA were antagonized by L-arginine (10(-3) M). The presence of neurons containing nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase was histochemically demonstrated in the sphincter of Oddi. These findings may indicate that TES, nicotine and K+ liberate NO from NANC inhibitory nerve which is involved in the relaxation of the dog sphincter of Oddi. The muscular tone does not seem to be regulated by cholinergic nerves under the experimental conditions used.

Role of nitric oxide in motility and secretion of the feline hepatobiliary tract

BACKGROUND

Nitric oxide (NO) mediates inhibition of gastrointestinal smooth-muscle cells via nonadrenergic, non-cholinergic (NANC) nervous pathways. The effect of NO on the absorption and secretion by the mucosa of the gastrointestinal and hepatobiliary tracts is less well known. The aim of this study was to evaluate the effects of a pharmacologic blockade of NO synthase on sphincter of Oddi activity, gallbladder function, and bile secretion and to demonstrate the presence of NO synthase-positive neurons in this region.

METHODS

Experiments were conducted on anesthetized cats after blockage of noradrenergic and cholinergic neurotransmission. Flow resistance in the sphincter of Oddi, gallbladder fluid absorption and motility, bile outflow from the liver, and bile salt secretion were registered.

RESULTS

Flow resistance exerted by the sphincter of Oddi increased dose-dependently in response to the NO synthase blocker NG-nitro-L-arginine. The increase in flow resistance was reversed stereospecifically by L-arginine, the substrate for NO synthesis. No significant effects on bile secretion, gallbladder fluid transport, or gallbladder motility were observed. NO synthase-positive neurons were identified close to the sphincter of Oddi and in the gallbladder mucosa.

CONCLUSIONS

This tonically active inhibitory NANC innervation of the sphincter of Oddi may be important in the physiologic regulation of the bile duct pressure.

Immunohistochemical identification of neurons in ganglia of the guinea pig sphincter of Oddi

The sphincter of Oddi is a smooth muscle sphincter that regulates the flow of bile into the duodenum. To identify potential chemical coding in sphincter of Oddi neurons, immunohistochemistry and histochemistry were employed to assay for putative neurotransmitters and related synthetic enzymes in wholemount preparations, with and without colchicine treatment. Immunoreactivities for enkephalin-endorphin (ENK-END), substance P (SP), nitric oxide synthase, vasoactive intestinal peptide (VIP), neuropeptide Y (NPY), and calcitonin gene-related peptide (CGRP) were demonstrated within the ganglionated plexus. Roughly half of the neurons in the sphincter of Oddi expressed immunoreactivity for both SP and ENK-END, but not for nitric oxide synthase. About 25% of the neurons expressed nitric oxide synthase immunoreactivity as well as NADPH-diaphorase activity. This contingent of neurons was made up of two subgroups: one that expressed immunoreactivity for VIP, the other for NPY. Neurons that expressed CGRP immunoreactivity were sparse in sphincter of Oddi ganglia; however, many axons immunoreactive for both CGRP and SP were present in the ganglionated plexus. The CGRP/SP fibers are probably visceral afferents that may influence ganglionic output through axon reflex circuits. These results, along with studies of the actions of these neuroactive compounds on sphincter tone, support the view that ganglia of the sphincter of Oddi are largely comprised of excitatory (SP/ENK-END-immunoreactive) and inhibitory (nitric oxide synthase/VIP- or NPY-immunoreactive) neurons, and that sphincter of Oddi tone is controlled by the regulation of the outputs of these two groups of cells.

Inhibition of sphincter of Oddi function by the nitric oxide carrier S-nitroso-N-acetylcysteine in rabbits and humans

Nitric oxide (NO) is an inhibitor of gastrointestinal smooth muscle. Model systems of the gut predict the NO will complex with biological thiol (SH) groups, yielding S-nitrosothiols (RS-NO), which may limit the propensity to form mutagenic nitrosamines. The inhibitory effects of NO and its biologically relevant adducts on sphincter of Oddi (SO) motility have been inferred from animal studies; however, their importance in regulating human SO is not known. The objectives of this study were to (a) provide histologic confirmation of nitric oxide synthase (NOS) in human SO; (b) characterize the pharmacology of S-nitroso-N-acetylcysteine (SNAC), an exemplary S-nitrosothiol, on SO motility in a rabbit model; and (c) study the effects of topical SNAC on SO motility in humans. Immunocytochemical and histochemical identification of NOS was performed in human SO. The pharmacologic response of SNAC was defined in isolated rabbit SO using a standard bioassay. Topical SNAC was then applied to the duodenal papilla in patients undergoing endoscopic retrograde cholangiopancreatography (ERCP) and biliary manometry. NOS was localized to nerve fibers and bundles of the SO in rabbits and humans. SNAC inhibited spontaneous motility (frequency and amplitude) as well as acetylcholine-induced elevations in SO basal pressure in the rabbit model. In patients undergoing ERCP and biliary manometry, topical SNAC inhibited SO contraction freqency, basal pressure, and duodenal motility. NOS is localized to neural elements in human SO, implicating a role for NO in regulating SO function. Supporting this concept, SNAC is an inhibitor of SO and duodenal motility when applied topically to humans during ERCP. Our data suggest a novel clinical approach using local NO donors to control gastrointestinal motility and regulate sphincteric function.