bluuebunny/crossref_metadata_2025 huggingface dataset:
Tyrosine kinase activities in the modulation of stimulated parietal cell acid secretion
Authors: Tsunoda Y. , Modlin I. M. , Goldenring J. R.
Published: December 2017

The effects of protein tyrosine kinase (PTK) activities on the modulation of secretion were investigated in isolated rabbit parietal cells. Two classes of inhibitors, genistein (an inhibitor of both soluble and membrane-associated PTK activities) and an erbstatin analogue (an inhibitor of membrane-associated PTK activities), were tested against both secretagogue stimulation as well as transforming growth factor-alpha (TGF-alpha) inhibition. Pretreatment of rabbit parietal cells with 10(-7) M rat TGF-alpha resulted in inhibition of both histamine- and carbachol-stimulated [14C]-aminopyrine (AP) accumulation. TGF-alpha inhibition was totally reversed by simultaneous pretreatment of cells with 50 microM genistein or an erbstatin analogue, indicating that a receptor-associated PTK activity is likely involved in the inhibition of parietal cell secretion. Furthermore, genistein, but not the erbstatin analogue, potentiated histamine-stimulated AP accumulation with a change in EC50 from 1.9 to 0.5 microM. Similarly, genistein, but not the erbstatin analogue, potentiated the response to forskolin with a change in EC50 from 1.5 to 0.1 microM. Genistein had no effect on stimulation of AP uptake by either dibutyryladenosine 3',5'-cyclic monophosphate or carbachol. In addition, genistein failed to increase histamine or forskolin stimulation beyond the maximal level and had no significant effect on either cellular adenosine 3',5'-cyclic monophosphate production or intracellular Ca2+ concentration. These results suggest that a PTK-protein phosphotyrosine phosphatase system may be involved in the potentiation of the histamine signal by a mechanism independent of adenylate cyclase activation.
Determinants of intrabolus pressure during esophageal peristaltic bolus transport
Authors: Ren J. , Massey B. T. , Dodds W. J. , Kern M. K. , Brasseur J. G. , Shaker R. , Harrington S. S. , Hogan W. J. , Arndorfer R. C.
Published: December 2017

Previous manometric studies of esophageal fluid bolus transport in humans have generally ignored the hydrodynamic distinction between intrabolus pressure and pressure within the lumen-occluded, contracting esophageal segment. In this study we obtained concurrent esophageal videofluoroscopic and intraluminal manometric recordings in supine normal volunteers using different bolus volumes and viscosities and abdominal compression. Intrabolus pressure increased with bolus volume, viscosity, and abdominal compression. Esophageal diameter increased with larger bolus volumes, and this increase was correlated with increases in intrabolus pressure. Intrabolus pressure was highest in the bolus tail. Peak intraluminal pressures > 20 mmHg above basal intrabolus pressure almost invariably were associated with effective peristalsis, whereas values of this pressure differential < 20 mmHg frequently were associated with ineffective peristalsis and retrograde bolus escape. Intrabolus pressure can serve as an important indicator of the forces resisting peristaltic transport and the occurrence of ineffective bolus transport.
Action of pituitary adenylate cyclase-activating polypeptide on ion transport in guinea pig distal colon
Authors: Kuwahara A. , Kuwahara Y. , Mochizuki T. , Yanaihara N.
Published: December 2017

The aim of the present study was to investigate the action of pituitary adenylate cyclase-activating polypeptide (PACAP) on ion transport in the guinea pig distal colon. Submucosal/mucosal segments from distal colon were mounted in Ussing flux chambers, and increases in short-circuit current (Isc) were used as an index of secretion. Serosal addition of PACAP-38 and PACAP-27 produced concentration-dependent (10(-10)-10(-6) M) increases in Isc. Furosemide and chloride-free solutions significantly reduced the PACAP-evoked responses. Tetrodotoxin (TTX) completely blocked PACAP-evoked responses. Atropine significantly reduced the PACAP-evoked responses but did not abolish the responses. The results suggest that PACAP evokes chloride secretion through cholinergic and noncholinergic neural mechanism. Vasoactive intestinal polypeptide (VIP), peptide histidine-isoleucine amide, and helodermin evoked Isc in a concentration-dependent manner. Atropine reduced but did not abolish the VIP- and related peptides-evoked responses. TTX also significantly decreased the responses to higher concentrations of VIP and related peptides but did not abolish the responses. The results suggest that VIP and related peptides act on both submucosal neurons and the epithelial cell itself. VIP tachyphylaxis significantly decreased PACAP-38- and PACAP-27-evoked responses. These results provide evidence that PACAP recognizes, in some part, VIP receptors in the submucosal neurons to evoke chloride secretion.
Elevation of cAMP facilitates noradrenergic transmission in submucous neurons of guinea pig ileum
Authors: Zafirov D. H. , Cooke H. J. , Wood J. D.
Published: December 2017

Slow synaptic excitation and inhibition were studied with intracellular microelectrodes in submucous ganglion cells of the guinea pig ileum. Elevation of adenosine 3',5'-cyclic monophosphate (cAMP) after application of forskolin or the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (IBMX) resulted in slowly activating depolarization of the membrane potential. The depolarization was associated with increased input resistance, enhanced excitability, and suppression of hyperpolarizing afterpotentials. This occurred in AH/type 2 but not S/type 1 neurons. The action of forskolin or IBMX mimicked slow synaptic excitation in the same neurons. Focal electrical stimulation also evoked slow inhibitory postsynaptic potentials (IPSPs). The amplitude and duration of the IPSPs were increased by forskolin or a membrane-permeant analogue of cAMP. Treatment with phentolamine, yohimbine or idazoxan suppressed the IPSPs before and after potentiation by forskolin, suggesting that the IPSPs were mediated by release of norepinephrine acting at alpha 2-adrenoceptors. Application of adenosine or selective adenosinergic A1 agonists suppressed or abolished the IPSPs. The results suggest that elevation of cAMP facilitates the release of norepinephrine at alpha 2-synapses on submucous neurons of guinea pig small bowel.
Intestinal permeability in allergic rats: nerve involvement in antigen-induced changes
Authors: Crowe S. E. , Soda K. , Stanisz A. M. , Perdue M. H.
Published: December 2017

In vivo uptake of the probe 51Cr-labeled EDTA from the jejunum of egg albumin (EA)-sensitized rats was compared with controls at baseline and after intraluminal antigen challenge. Probe recovery in blood was 60-80% greater in sensitized animals during the baseline period, suggesting that sensitization resulted in increased intestinal permeability. Sensitized, but not control, rats demonstrated a 15-fold increase in 51Cr-EDTA uptake after intraluminal antigen; no change occurred with an unrelated protein. Macromolecular recovery was also enhanced in sensitized animals, since serum levels of immunoreactive EA were elevated 14-fold compared with controls. Antigen challenge was accompanied by biochemical (protease release) and morphological (reduced numbers) evidence of mast cell degranulation in sensitized rats. The neurotoxin tetrodotoxin (applied directly to ligated jejunal segments) inhibited EA-induced uptake of 51Cr-EDTA and antigen. In isolated jejunum from sensitized rats, tetrodotoxin reduced secretory responses to luminal, but not serosal, antigen. These results indicate that neural factors may influence the uptake of molecules from the gut lumen during intestinal anaphylaxis.
Stimulus-associated protein in gastric parietal cell detected using antimelittin antibody
Authors: Cuppoletti J. , Huang P. , Kaetzel M. A. , Malinowska D. H.
Published: December 2017

The bee venom polypeptide melittin binds to and inhibits the gastric hydrogen-potassium-adenosinetriphosphatase (H(+)-K(+)-ATPase). A search for parietal cell proteins with a melittin-like structure was carried out. A 67-kDa (doublet) protein, which reacted with a polyclonal antimelittin antibody, was found in purified rabbit parietal cells. The protein exhibited reversible stimulus-dependent redistribution from cytosol to (total) membranes. It was also found to be associated with H(+)-K(+)-ATPase-containing membranes when isolated from the gastric mucosae of rabbits treated with histamine, but not with cimetidine. The presence of the protein correlated with the ability of the membrane preparations to exhibit ionophore-independent HCl accumulation, a characteristic of gastric membranes from histamine-stimulated animals. The 67-kDa melittin-like protein may play a role in the functional changes in the gastric parietal cell that are involved in stimulation of HCl secretion.
Defective modulation of colonic secretomotor neurons in a rabbit model of colitis
Authors: Goldhill J. M. , Burakoff R. , Donovan V. , Rose K. , Percy W. H.
Published: December 2017

The present in vitro study was conducted to investigate possible alterations in the control of colonic electrolyte transport in an experimental model of colitis. Intrarectal administration of trinitrobenzenesulfonic acid induced a colitis-like inflammation in the rabbit distal colon. Responses to amiloride and residual short-circuit current after this treatment were unchanged, suggesting that the absorptive and secretory mechanisms remained intact. Electrical field stimulation and vasoactive intestinal polypeptide, a candidate secretomotor neurotransmitter, both elicited similar responses in control and colitic tissue. This suggests that communication at the neuroepithelial junction was unimpaired. In untreated tissue, the effects of prostaglandin E2 (PGE2) and of acetylcholine were attenuated by tetrodotoxin, suggesting, therefore, that both play a role in the modulation of secretomotor neurons. In addition, PGE2 had an appreciable direct epithelial effect. Responses to both of these agonists were absent in colitis. The effects of N6,2'-O-dibutyryladenosine 3',5'-cyclic monophosphate were unchanged in colitis, suggesting that altered PGE2 responsiveness may involve changes in epithelial receptor number, affinity, or in their ability to mediate an increase in adenosine 3',5'-cyclic monophosphate levels. It is concluded that this rabbit model of colitis exhibits 1) defects in the modulation of secretomotor neurons by acetylcholine and PGE2 and 2) an attenuated epithelial response to PGE2.
Involvement of cAMP and cGMP in relaxation of internal anal sphincter by neural stimulation, VIP, and NO
Authors: Chakder S. , Rattan S.
Published: December 2017

We examined simultaneous changes in resting tension and tissue levels of the two second messengers, adenosine 3',5'-cyclic monophosphate (cAMP) and guanosine 3',5'-cyclic monophosphate (cGMP), in the opossum internal anal sphincter (IAS). The influence of the nonadrenergic noncholinergic (NANC) nerve stimulation (NS) by electrical field stimulation (EFS) and the putative neurotransmitters nitric oxide (NO) and vasoactive intestinal peptide (VIP) on the above modalities was investigated. The fall in resting IAS tension in response to NS, NO, and VIP was accompanied by significant rises in both cGMP and cAMP. This fall and the levels of cAMP and cGMP were dependent on the intensity of EFS and the concentration of VIP and NO. EFS (2 Hz) caused a 63.5% fall of the resting tension with 61.7 and 118.2% rise of the tissue levels of cAMP and cGMP, respectively (P < 0.05). VIP (1 x 10(-6) M) caused an 81.5% fall of resting tension and 64.2 and 87.0% increases in cAMP and cGMP, respectively. Similarly, NO (1 x 10(-6) M) caused 69.6% fall in tension and an accompanying 93.4 and 415.9% rise of cAMP and cGMP, respectively. Although EFS, VIP, and NO all lowered IAS tension and raised both cyclic nucleotides, the changes in cAMP and cGMP in the IAS are otherwise stimulus specific, since fall in IAS tension by calcitonin gene-related peptide has been shown to be associated with an increase in cAMP without any change in cGMP, whereas the reverse was the case with atrial natriuretic factor. The common second messenger systems in IAS relaxation with NS, VIP, and NO suggest the involvement of VIP and NO as inhibitory neurotransmitters.
Downregulation of neutral endopeptidase (EC 3.4.24.11) in the inflamed rat intestine
Authors: Hwang L. , Leichter R. , Okamoto A. , Payan D. , Collins S. M. , Bunnett N. W.
Published: December 2017

Intestinal inflammation induced by the nematode Trichinella spiralis is accompanied by increased intestinal concentrations of substance P, a mediator of inflammation and a stimulant of smooth muscle contraction, and by intestinal hypermotility. The expression of neutral endopeptidase (NEP), a cell surface enzyme that degrades substance P in the extracellular fluid, was examined in the inflamed intestine. NEP enzymatic activity, measured by a fluorometric assay, was reduced by 84-fold in jejunal mucosa-circular muscle and by 12-fold in jejunal longitudinal muscle-myenteric plexus within 6 days after infection with T. spiralis. The downregulation was unaffected by treatment with betamethasone and was still observed in athymic animals. NEP protein levels, examined by Western blotting, confirmed the loss of NEP from inflamed tissue. The specific activity for degradation of substance P was reduced by sixfold in jejunal mucosa-circular muscle and by twofold in jejunal longitudinal muscle-myenteric plexus of rats infected with T. spiralis compared with uninfected controls. Thus the downregulation of NEP resulted in reduced substance P degradation, which may contribute to functional abnormalities of the inflamed intestine.
Gastric axial forces in experimentally delayed and accelerated gastric emptying
Authors: Prather C. M. , Camilleri M. , Thomforde G. M. , Forstrom L. A. , Zinsmeister A. R.
Published: December 2017

The aim of this study was to assess the relationship between altered axial forces and gastric emptying of solids by experimentally inhibiting or stimulating gastric axial forces by intraduodenal lipid or intravenous erythromycin, respectively. In 15 healthy volunteers, we simultaneously measured gastric emptying of solids by scintigraphy, gastroduodenal motility by manometry, and forces along the longitudinal axis of the distal stomach by an axial force transducer. When 25% of the radiolabel had emptied from the stomach, subjects (n = 5 in each group) received normal saline (controls), intraduodenal lipid, or intravenous erythromycin. The test period consisted of the infusion period (10 min) and the subsequent 30 min. Lipid significantly reduced and erythromycin increased axial forces compared with control (lipid: median 0.6 N [0-1.4 interquartile range (IQR)]; erythromycin: median 18.2 N (16.5-20.5 IQR); control: median 4.7 N (3.9-5.2 IQR); P < 0.01). Similarly, antral phasic pressure activities were different relative to control. Gastric axial forces correlated significantly with gastric emptying (Spearman rank correlation = 0.86; P < 0.01). These data are consistent with the hypothesis that axial forces affect gastric emptying of solids and suggest that measurement of axial forces provides an assessment of overall gastric propulsion during the emptying of solids.
Mitogenic activity of rat salivary glands after electrical stimulation of parasympathetic nerves
Authors: Schneyer C. A. , Humphreys-Beher M. G. , Hall H. D. , Jirakulsomchok D.
Published: December 2017

Electrical stimulation of the parasympathetic innervation to parotid or submandibular gland for 30 or 60 min resulted in increased [3H]thymidine uptake of both glands when measurements were made 18 h later. With 30 min of stimulation, the mean increase in parotid was 30% compared with unstimulated mates, and after 60 min of stimulation, the increase was 76%. Stimulation for 30 min with the adrenergic antagonists propranolol and phenoxybenzamine present showed an increase in [3H]thymidine of 76%. Stimulation of the chorda tympani for 30 min resulted in a mean increase of 59% in thymidine uptake of the sympathectomized submandibular gland compared with the unstimulated sympathectomized mate. beta-1,4-Galactosyltransferase activity of both stimulated parotid and submandibular glands also showed an increase of 71%. On the basis of the composition of the saliva in the oral cavity, we confirmed the identity of the stimulated nerve to parotid gland as the parasympathetic (auriculotemporal). Na, K, and amylase concentrations resembled closely the composition of saliva obtained directly from the duct with electrical stimulation of the parasympathetic nerve. These data provide the first evidence that electrical stimulation of the parasympathetic nerve to parotid and submandibular glands causes a mitogenic response in each of these organs; the data also provide the first evidence that electrical stimulation of the parasympathetic nerve causes an increase in levels of the enzyme beta-1,4-galactosyltransferase, known to be implicated in hyperplastic responses.
Activation of whole cell currents in isolated human jejunal circular smooth muscle cells by carbon monoxide
Authors: Farrugia G. , Irons W. A. , Rae J. L. , Sarr M. G. , Szurszewski J. H.
Published: December 2017

Carbon monoxide (CO) is a low molecular weight oxide produced endogenously from fatty acids and heme protein. A physiological role for CO has been suggested for vascular smooth muscle, hemostasis, and olfactory neurons, but direct evidence is lacking. Heme oxygenase, which catalyzes the formation of CO from heme proteins, is present in small intestinal smooth muscle. The effect of 1% CO on whole cell currents in normal human jejunal circular muscle cells was studied with the use of a perforated patch-clamp technique. A 1% CO-containing Krebs solution caused an initial and transient increase in whole cell current in 20 of 22 cells tested (175 +/- 40%, mean +/- SE) and a transient hyperpolarization (15.6 +/- 3.6 mV, mean +/- SE) of the membrane potential. During prolonged recordings, 1% CO evoked ongoing cyclic increases and decreases in the whole cell current. Each current increase was accompanied by a sharp membrane hyperpolarization. These data suggest that CO may modulate whole cell potassium current and membrane potential.
Electrogenicity of Na-coupled bile salt transport in isolated rat hepatocytes
Authors: Weinman S. A. , Weeks R. P.
Published: December 2017

The importance of membrane voltage in uptake of bile salts into hepatocytes is not known. Electrogenicity of the primary bile salt transport process, Na-bile salt cotransport, has been difficult to determine because the large K and Cl conductances of the sinusoidal membrane (GK and GCl, respectively) obscure any transport associated currents. In the present study hepatocytes were treated to reduce these membrane conductances and electrogenic entry of taurocholate and glycocholate was demonstrated. Intracellular voltage and resistance changes resulting from bile salt transport were measured in hepatocytes in which GK and GCl were blocked by impalement with Na acetate microelectrodes and external exposure to quinine (400 microM). This increased the cell input resistance from 153 +/- 17 to 230 +/- 17 M omega (n = 14, P < 0.001). Under these conditions, exposure to 100 microM of taurocholate or glycocholate produced Na-dependent depolarizations of 3.0 +/- 0.5 and 4.2 +/- 0.8 mV, respectively. These correspond to transport currents of 13.9 and 7.6 pA/cell, which are comparable to those predicted from known [3H]taurocholate uptake rates if one positive charge enters the cell with each bile salt molecule. Although uptake of these two bile salts was electrogenic, this was not the case for all bile salts. Na-dependent transport of taurodehydrocholate, which occurs at similar rates to that for taurocholate, produced no voltage change. The unconjugated bile salts cholate and ursodeoxycholate also produced no measurable voltage or resistance changes. In conclusion, Na-dependent uptake of taurocholate and glycocholate is electrogenic, whereas uptake of taurodehydrocholate, ursodeoxycholate, and cholate is predominantly electroneutral.(ABSTRACT TRUNCATED AT 250 WORDS)
Characterization of Na(+)-independent glutamine transport in rat liver
Authors: Pacitti A. J. , Inoue Y. , Souba W. W.
Published: December 2017

In hepatic plasma membrane vesicles (HPMVs) from rat liver, we observed that approximately 40-45% of Na(+)-independent glutamine uptake occurs by a saturable carrier-mediated process. This component of glutamine uptake is mediated by a transport agency distinct from that of previously described systems for the Na(+)-independent transport of amino acids. Transport of glutamine was electroneutral and occurred into an osmotically active space with negligible membrane binding. The model system L substrate 2-amino-2-norbornane-carboxylic acid (BCH) showed no appreciable inhibition of Na(+)-independent glutamine uptake by HPMVs but effectively inhibited the uptake of leucine, a classic system L substrate, in identical vesicle preparations. Further evidence against system L-mediated glutamine transport was provided by the pH dependence and the lack of trans-stimulation of saturable uptake. Competition experiments with selected amino acids revealed a pattern of inhibition of glutamine transport that was inconsistent with assignment of glutamine entry to systems asc, T, or systems for the Na(+)-independent transport of the charged amino acids. This BCH-noninhibitable transport system in HPMVs was highly selective for glutamine, histidine, and, to a lesser extent, asparagine. Inhibition of Na(+)-independent glutamine transport by leucine was noncompetitive in nature. On the basis of Na+ independence, pH sensitivity, absence of trans-stimulation, and an amino acid selectivity similar to that of the previously described hepatic Na(+)-dependent system N, we have provisionally designated the glutamine transport agency described in this article as system "n."
Somatostatin inhibits pancreatic enzyme secretion at a central vagal site
Authors: Li Y. , Owyang C.
Published: December 2017

The mechanisms and site of action of somatostatin-induced inhibition of pancreatic enzyme secretion were investigated using different stimulants of pancreatic secretion acting on different sites in anesthetized rats. Administration of graded doses of somatostatin-14 resulted in a dose-related inhibition of pancreatic protein secretion evoked by 2-deoxy-D-glucose, a central vagal stimulant that acts by stimulating the dorsal vagal nuclei. The lowest effective dose of somatostatin-14 was 1.0 microgram.kg-1 x h-1; maximal effective dose was 25 micrograms.kg-1 x h-1, which resulted in complete inhibition of protein output. Similarly, somatostatin-14 at a dose of 25 micrograms.kg-1 x h-1 also completely inhibited pancreatic protein secretion in response to a physiological concentration of cholecystokinin octapeptide (CCK-8), which acts via a vagal afferent pathway. In contrast, pancreatic protein outputs evoked by bethanechol, which directly stimulates pancreatic muscarinic receptors, or electrical stimulation of the vagal trunk, which activates the vagal efferent pathway, were unaffected by somatostatin-14. In separate studies, we demonstrated that perivagal treatment with the sensory neurotoxin capsaicin impaired pancreatic responses to CCK-8 but had no effect on the inhibitory action of somatostatin-14 on pancreatic secretion evoked by 2-deoxy-D-glucose, ruling out an effect of somatostatin on the vagal afferent pathway. Similarly we also demonstrated that perineural capsaicin treatment of the celiac-superior mesenteric ganglia did not affect the inhibitory action of somatostatin. These findings indicate that somatostatin inhibits 2-deoxy-D-glucose- and CCK-8-evoked pancreatic enzyme secretion via a vagal pathway.(ABSTRACT TRUNCATED AT 250 WORDS)
Influence of tactile stimulation of the rat gastric mucosa on blood flow and acid output
Authors: Holm L. , Jagare A.
Published: December 2017

The influence of tactile stimulation of the gastric mucosa (mimics the mechanical influence of the food bolus) on the gastric mucosal blood flow and acid output was studied in rats anesthetized with Inactin. Blood flow was measured with laser-Doppler flowmetry (LDF) with the probe positioned above the gastric mucosa, and acid secretion was measured at regular intervals by titration of the saline covering 0.8 cm2 of the mucosa. After gentle tactile stimulation (wiping with cotton tips) of the mucosa for 20 s, blood flow increased to approximately 250% of the control value and then returned to the control level 15 min later, whereas acid output was transiently reduced immediately after tactile stimulation. Pretreatment with lidocaine, methysergide, or hexamethonium did not change the results of tactile stimulation on the blood flow. After indomethacin (3 mg/kg i.v.) LDF was significantly reduced by 33% and the hyperemic response to tactile stimulation was almost abolished. This suggests that endogenously released prostaglandins, not evoked through activation of intramural reflexes that can be blocked by lidocaine, methysergide or hexamethonium, are responsible for the hyperemia seen after tactile stimulation of the gastric mucosa.
Intracellular alkalinization stimulates bile flow and vesicular-mediated exocytosis in IPRL
Authors: Bruck R. , Benedetti A. , Strazzabosco M. , Boyer J. L.
Published: December 2017

Intracellular pH recovery from an acute alkaline load in rat hepatocytes is mediated by a Cl(-)-HCO3- exchanger, which is electroneutral, Na+ independent, and 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) sensitive. Stimulation of this Cl(-)-HCO3- exchanger requires intact microtubules, suggesting that vesicular transport may be required to activate this exchanger. To determine if intracellular alkalinization stimulates biliary HCO3- excretion and bile flow in the intact liver by vesicle-mediated exocytosis, isolated perfused rat livers (IPRL) were alkalinized by two protocols. Isohydric changes in CO2 and HCO3- concentrations induced transient increases in bile flow by 36% (P < 0.01), which were abolished by DIDS (0.01 mM), inhibited by pretreatment with colchicine (P = 0.01), but not affected by membrane depolarization with the K(+)-channel blocker BaCl2 (1 mM). Similarly, perfusion with 20 mM NH4Cl produced a 42% increase in bile flow (P < 0.01) and a 26% increase in biliary HCO3- excretion. Both the increases in bile flow and HCO3- excretion were almost completely blocked by DIDS and inhibited by pretreatment with colchicine (P < 0.01). Biliary excretion of horseradish peroxidase was also increased during intracellular alkalinization with either protocol (P < 0.01). These findings suggest that intracellular alkalinization stimulates bile flow and biliary HCO3- excretion. Microtubule-dependent vesicular-mediated exocytosis is involved in this response.
Preserved organic anion transport in mutant TR- rats with a hepatobiliary secretion defect
Authors: Jansen P. L. , van Klinken J. W. , van Gelder M. , Ottenhoff R. , Elferink R. P.
Published: December 2017

The in vivo biliary secretion of a number of organic anions in mutant TR- rats was studied. The secretion of bilirubin glucuronide (BG), the glutathione conjugate of bromosulfophthalein, dibromosulfophthalein, and indocyanine green was reduced to 2, 15, 50, and 75% of normal, respectively. Surprisingly, the secretion of bilirubin ditaurate (BDT) was entirely normal under these conditions. In isolated TR- rat liver perfusion experiments (recirculating setup), the hepatobiliary secretion of BG and BDT was reduced to 1 and 50% of normal, respectively. There was considerable residual concentrative transport of BDT under these conditions (bile-to-perfusate concentration ratio of 190 +/- 60; normal, 730 +/- 480), whereas for BG the concentration step was completely abolished (bile-to-perfusate concentration ratio of 1.3 +/- 1.0; normal, 60 +/- 40). In a single-pass isolated TR- rat liver perfusion study, BDT secretion after bolus administration (1 mumol) was abnormal; the peak secretion was retarded to 20 min after injection (normal 7.5 min), and the secretion rate was decreased to 19% of normal. BDT, as an organic dianion, is a substrate for the "canalicular multispecific organic anion transporter" (cMOAT), a carrier protein that is defective in TR- rats. Its considerable residual secretion in certain experimental conditions suggests the preservation of a low-affinity pathway for secretion of some cMOAT substrates in TR- rats.
Role of endogenous endothelin in pathogenesis of ethanol-induced gastric mucosal injury in rats
Authors: Masuda E. , Kawano S. , Nagano K. , Tsuji S. , Takei Y. , Hayashi N. , Tsujii M. , Oshita M. , Michida T. , Kobayashi I. , et al.
Published: December 2017

The major objective of this study was to elucidate the role of endogenous endothelin (ET)-1, a potent vasoconstrictor peptide, in the pathogenesis of ethanol (EtOH)-induced gastric mucosal injury. Two series of experiments were performed in anesthetized rats. First, we examined the time course of relationships among changes in ET-1 concentrations in gastric mucosal and portal plasma, gastric mucosal hemodynamics, and mucosal damage produced by EtOH. Intragastric EtOH stimulated release of endogenous ET-1 in gastric mucosal tissue. Plasma ET-1 concentrations in the portal vein also increased after intragastric EtOH administration. ET-1 concentrations in gastric mucosal tissue and portal plasma increased significantly before gastric mucosal hemorrhagic damage occurred. Moreover, 30 min after EtOH administration there were significant correlations between gastric mucosal ET-1 concentrations and both area of gastric hemorrhagic damage as well as concentration of EtOH administered intragastrically. After intragastric EtOH administration, increase in gastric mucosal hemoglobin concentration and decrease in gastric mucosal hemoglobin oxygen saturation, estimated using reflectance spectrophotometry, occurred within 2.5 min and continued throughout the experiments. The time course of microcirculatory changes correlated closely with increases in gastric mucosal ET-1 and portal plasma ET-1 concentrations after intragastric EtOH administration. Gastric microcirculatory disturbances induced by EtOH were associated with significant decreases in gastric mucosal ATP content. Second, we examined whether pretreatment with anti-ET-1 antibody protected against EtOH-induced mucosal injury by improving mucosal microcirculation. Pretreatment with anti-ET-1 antibody microscopically and macroscopically reduced gastric mucosal hemorrhagic damage induced by EtOH and significantly reduced EtOH-induced gastric microcirculatory disturbances and decreases in gastric mucosal ATP.(ABSTRACT TRUNCATED AT 250 WORDS)
Mechanism of action of CCK in avian gastroduodenal motility: evidence for nitric oxide involvement
Authors: Martinez V. , Jimenez M. , Gonalons E. , Vergara P.
Published: December 2017

Our objective was to study the mechanism of action of cholecystokinin (CCK) on the motility of the gastroduodenal area. Chickens were implanted with five electrodes for electromyography in the stomach and duodenum. The effects of CCK (10(-9) mol.kg-1.10 min-1) were studied against the presence of several antagonists and in vagotomized animals. CCK caused inhibition of gastric motility and duodenal hyperactivity. Vagotomy blocked CCK responses in the stomach but not in the duodenum. Hexamethonium partially blocked gastric inhibition induced by CCK. NG-nitro-L-arginine methyl ester blocked the inhibitory response to CCK in the stomach but did not modify duodenum response. L-Arginine did not modify CCK actions. Opioid antagonists naloxone and naltrindole and adrenergic antagonists phentolamine and propranolol did not modify CCK response. Atropine did not modify duodenal response to CCK. Sodium nitroprusside (10(-8)-10(-6) mol/kg) inhibited gastroduodenal activity in a dose-related manner. We suggest that gastric response to CCK is vagally mediated, mainly by the nitric oxide system. Duodenal hyperactivity seems to be a direct action of CCK. Nitric oxide is a putative neurotransmitter in the chicken gut.
Intracellular pH-regulating ion transport mechanisms in parietal cell basolateral membrane vesicles
Authors: Lamprecht G. , Seidler U. , Classen M.
Published: December 2017

Na(+)-H+ and Cl(-)-base exchangers on the parietal cell have been demonstrated by several authors. Controversy exists concerning a basolateral Na(+)-HCO3- cotransporter in the parietal cell. To clarify this issue, we prepared highly enriched basolateral membrane (BLM) and apical-tubulovesicular membrane (to serve as negative controls) vesicles from rabbit fundic mucosa. Na(+)-H+ exchange was demonstrated by measuring pH gradient-driven amiloride-sensitive 22Na+ uptake and Na+ gradient-driven proton uptake into voltage-clamped BLM but not into apical-tubulovesicular vesicles. Anion exchange was demonstrated by measuring 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS)-inhibitable influx of 36Cl- into Cl(-)- or HCO3(-)-loaded voltage-clamped BLM vesicles. Na(+)-HCO3- cotransport was assessed by comparing HCO3(-)-driven 22Na uptake with uptake driven by an identical pH gradient. No significant difference was found between 22Na uptake in the presence and absence of HCO3-; 1 mM amiloride inhibited 22Na uptake > 90% in both conditions, whereas 2 mM DIDS had no effect. In BLM vesicles prepared from rabbit renal cortex, however, a HCO3- gradient stimulated 22Na uptake much more than an equivalent pH gradient, and DIDS inhibited this HCO3- gradient-driven 22Na uptake. This indicates that our experimental setup was suitable to detect a Na(+)-HCO3- cotransporter if present. Our data suggest that the parietal cell BLM contains Na(+)-H+ exchangers and Cl(-)-HCO3- exchangers but no Na(+)-HCO3- cotransporter.
Interaction of bumetanide derivatives with hepatocellular bile acid uptake
Authors: Petzinger E. , Follmann W. , Blumrich M. , Schermuly R. , Schulz S. , Hahnen J. , Feit P. W.
Published: December 2017

The loop diuretic bumetanide is an organic monocarboxylic organic anion assumed to be transported into hepatocytes by a transport system for bile acids. The structural requirements of 22 bumetanide analogues were analyzed for an interaction with bile acid uptake into isolated rat hepatocytes. Whereas bumetanide inhibited the hepatocellular uptake of [14C]cholate to the same degree as its own uptake, derivatization altered affinity and specificity and yielded compounds that selectively inhibited either cholate or taurocholate uptake or uptake of both. No correlation was found between the diuretic potency of bumetanide derivatives, reflecting the affinity to the Na(+)-K(+)-Cl- cotransporter, and their affinity to hepatic bile salt transport. Computer-aided model building combined with the calculation of potential energy maps showed a strictly amphipathic charge separation in bumetanide analogues as in bile acids. Ranking bumetanide compounds by their mean inhibitory concentration values, inhibition constants, and their type of competition, we conclude that at least three binding domains in the proteins are essential for recognition by bile acid transporters, namely two hydrophobic and an anionic side, and that for the anionic binding region a carbonyl atom in the ligands as an electron donor group is sufficient for ligand interaction.
Pressure diuresis and natriuresis in cirrhotic rats
Authors: Atucha N. M. , Cegarra M. , Ramirez A. , Quesada T. , Garcia-Estan J.
Published: December 2017

Arterial hypotension in liver cirrhosis has been proposed as a major mechanism contributing to renal sodium and water retention. To evaluate kidney excretory responses at different levels of arterial pressure (AP), we have characterized the relationships between renal perfusion pressure (RPP) and sodium and water excretion in carbon tetrachloride cirrhotic rats. Experiments were performed in anesthetized control (n = 9) and cirrhotic rats with (Asc, n = 6) and without ascites (Cir, n = 6) by mechanically adjusting vascular resistance in animals with renal denervation and infused with main systemic hormones. Control and Cir animals showed similar glomerular filtration rates (GFR), renal blood flows, hematocrits (Hct), and plasma proteins (PP). However, Hct, PP, and GFR were significantly lower in the Asc rats. For the same level of RPP, both cirrhotic groups excreted significantly less water and sodium than controls. Then, the pressure diuresis and natriuresis relationships of the Cir animals were significantly depressed, but those of the Asc animals were more reduced than those of the Cir rats. These results indicate that the cirrhotic kidney is not able to normally increase the sodium and water excretion in response to changes in AP. Intrarenal mechanisms, and not mainly RPP, are likely mediators of the renal alterations of liver cirrhosis.
Neural mediation of cholera toxin-induced mucin secretion in the rat small intestine
Authors: Moore B. A. , Sharkey K. A. , Mantle M.
Published: December 2017

We examined the role of enteric nerves in cholera toxin (CT)-induced mucin secretion in proximal and distal regions of rat small intestine. Stimulation of intestinal loops with 120 micrograms (1.5 mumol) CT using an in vitro open-loop model resulted in an approximately four-fold increase in luminal mucin content over unstimulated controls in both regions of the gut. Prior treatment of loops with tetrodotoxin had no effect on the amount of mucin released in response to CT. However, permanent destruction of primary sensory afferent nerves by neonatal treatment of rats with capsaicin reduced the mucin response to CT to baseline levels in both regions. In normal animals, atropine resulted in approximately 40% inhibition of mucin secretion in both the proximal and distal small intestine. The atropine-sensitive secretory response appears to be a component of the capsaicin-sensitive response. These results suggest that choleraic mucin secretion is mediated primarily by a capsaicin-sensitive neurogenic pathway involving local activation of sensory nerves, which may then elicit mucin secretion through interaction with cholinergic nerves.
Role of nitric oxide in esophageal peristalsis
Authors: Anand N. , Paterson W. G.
Published: December 2017

In vitro studies have suggested that NO may be a nonadrenergic, noncholinergic inhibitory mediator in the esophageal body. We examined the role of NO in physiological peristalsis in anesthetized opossums by assessing the effect of the NO synthase inhibitor N omega-nitro-L-arginine methyl ester (L-NAME) on esophageal contractions induced by swallows, prolonged vagal efferent nerve stimulation, and midesophageal balloon distension. A perfused manometry system measured intraluminal pressures 1 and 5 cm orad to the lower esophagus, and suction electrodes monitored membrane potential changes at the same locations. NO synthase inhibition 1) decreased swallow-induced contraction amplitude in the distal esophagus and, when combined with atropine, abolished these contractions; 2) diminished swallow-induced contraction latencies, predominantly in the distal esophagus, thereby decreasing the latency gradient and increasing the peristaltic velocity; 3) abolished vagal-stimulation-induced, end-of-stimulus “B” contractions and either unmasked or increased the amplitude of intrastimulus “A” contractions; 4) abolished the contractions occurring at the end of balloon distension; and 5) inhibited the membrane hyperpolarization and the subsequent nonadrenergic, noncholinergic depolarization induced by all three stimuli. These data support the hypothesis that NO is a mediator of nonadrenergic, noncholinergic neurotransmission in the opossum esophagus. Furthermore, the data suggest that esophageal peristalsis is mediated by a “blended” activation of cholinergic and nonadrenergic, noncholinergic (via NO) neurons
Rheogenic Cl- conductance and Cl(-)-Cl(-)-exchange activities in guinea pig jejunal basolateral membrane vesicles
Authors: Touzani K. , Cauzac M. , Vasseur M. , Alvarado F.
Published: December 2017

We describe a method for the simultaneous purification of apical (brush-border membrane) and basolateral membrane (BLM) vesicles from the same sample of guinea pig jejunum. We applied functional tests to demonstrate the absence of reciprocal cross contamination between the two vesicle preparations. By using the BLM vesicles and a rapid filtration technique, we quantified 36Cl uptake under conditions of equilibrated pH (pHout = pHin = 7.5). The presence of 200 mM cis of either Na+ or K+, or an equimolar mixture of both, significantly increased the initial Cl- entry rate. In the presence of K+, valinomycin further increased Cl- uptake, but no Cl- uphill transport was ever observed under any of the conditions. All the increases were abolished by voltage clamping, indicating that the alkali-metal ions act by creating an inside-positive membrane potential capable of stimulating a Cl(-)-conductance pathway. In the absence of K+, BLM vesicle preloading to obtain a [Cl-]out/[Cl-]in = 16/200 mM gradient (delta Cl-) resulted in a 500% increase in the initial 36Cl- entry rate, accompanied by a transient Cl- accumulation, with an overshoot at approximately 5 min. In the presence of both a positive-inside electrical gradient (delta psi) and a delta Cl-, the initial Cl- uptake rate was increased by 800%, indicating that the effects of delta psi and of delta Cl- are additive. The delta Cl- effect was blocked, but only partially, by short-circuiting the membrane potential with equilibrated K+ and valinomycin, thus indicating that it has both rheogenic and electroneutral components. We conclude that Cl- influx across the guinea pig intestinal BLM involves a Cl(-)-conductance pathway plus a distinct Cl(-)-Cl(-)-exchange system, exhibiting both electroneutral and rheogenic components. Alternatively, the possibility can also be entertained that the conductance and the exchange pathways share a common molecular basis, e.g., a nonobligatory Cl(-)-Cl- exchanger or rheogenic uniport.
Effect of sugars and amino acids on amphibian intestinal ClŐ transport and intracellular Na+, K+, and ClŐ activity
Authors: White J. F. , Burnup K. , Ellingsen D.
Published: December 2017

Pages G109–G117: J. F. White, K. Burnup, and D. Ellingsen. “Effect of sugars and amino acids on amphibian intestinal Cl- transport and intracellular Na+, K+, and Cl- activity.” Page G109 (abstract, 20th line): the sentence that reads “Galactose and valine each reduced intracellular Na Activity (agrNai) markedly, whereas glucose increased agrNai only slightly” should read “Galactose and valine each increased intracellular Na activity (agrNai) markedly, whereas glucose increased agrNai only slightly.”
Characterization of emulsions and lipolysis of dietary lipids in the human stomach
Authors: Armand M. , Borel P. , Dubois C. , Senft M. , Peyrot J. , Salducci J. , Lafont H. , Lairon D.
Published: December 2017

Fasting subjects were intragastrically intubated and received a coarsely emulsified test meal. Gastric aspirates were collected after 1, 2, 3, and 4 h. During digestion in the stomach, unemulsified lipids (> or = 100 microns) represented a minor fraction. A significant amount of the large 70- to 100-microns lipid droplets disappeared, and fine 1- to 10-microns droplets were generated. The median lipid droplet diameter significantly decreased (21.9 vs. 52.9 microns) after 1 h and kept intermediate values for longer periods of time. The emulsion surface area was 100-120 m2/l and was basically provided by 1- to 100-microns droplets. Lipolysis catalyzed by gastric lipase primarily occurred within the first hour of digestion (11.9%). Smaller droplets were enriched in triglyceride lipolytic products. The free fatty acid concentrations were in the range of 5.6-8.2 mM over 1-4 h. The present finding demonstrates for the first time that in the human stomach most dietary lipids are present in the form of emulsified droplets, in the range of 20-40 microns, and that gastric lipolysis can help to increase emulsification in the stomach.
Calcium efflux from an intracellular pool activated by GTP hydrolysis in cultured gastric smooth muscle
Authors: Gilbert R. J. , Khalid M.
Published: December 2017

In these studies, we have characterized calcium movement due to guanosine triphosphate (GTP) hydrolysis from an ATP-sequestered intracellular calcium pool in cultured gastric smooth muscle. GTP (1-100 microM), when added to an ATP-regenerating medium, resulted in a concentration-dependent and irreversible efflux of calcium from an organellar calcium pool. GTP-induced calcium efflux was not affected by variation of the ATP/ADP ratio (8.5-155.0), indicating that GTP did not act by inhibiting calcium influx via calcium adenosinetriphosphatase. To assess whether the calcium increase was necessarily associated with GTP hydrolysis, experiments were performed with the nonhydrolyzable guanine nucleotide analogues guanosine 5'-[beta-thio]diphosphate (GDP beta S), 5'-guanylyl imidodiphosphate guanosine (GppNHp), and 5'-O-(3-thiotriphosphate) (GTP gamma S). Administration of GDP beta S and GppNHp resulted in no significant calcium efflux. GTP gamma S caused a small steady-state calcium increase (20% of that induced by the hydrolyzable nucleotide) but irreversibly inhibited all subsequent calcium increase due to GTP. The possibility that GTP may either modify the concentration of mobilizable calcium in inositol trisphosphate (IP3)-sensitive calcium stores or the responsivity of IP3-associated calcium channels was assessed by two experiments: 1) prior administration of GTP at concentrations < or = 100 microM had no effect on IP3-induced calcium release, and 2) heparin, which competitively inhibits IP3 binding to its receptor on the endoplasmic reticulum, did not affect GTP-associated calcium increase. These results demonstrate that, in gastric smooth muscle, GTP causes calcium efflux from an intracellular pool that is functionally independent from that pool sensitive to IP3.(ABSTRACT TRUNCATED AT 250 WORDS)
Neurohormonal regulation of histamine synthesis in isolated rabbit fundic mucosal cells
Authors: Hollande F. , Bali J. P. , Magous R.
Published: December 2017

In a population of rabbit fundic mucosal cells enriched in mucous and endocrine cells, gastrin and cholecystokinin octapeptide (CCK-8) were shown to increase dose-dependently histidine decarboxylase (HDC) activity with the same efficacy and high potencies [50% effective concentration (EC50) 0.389 +/- 0.041 and 0.275 +/- 0.011 nM, respectively], whereas pentagastrin was less potent (EC50 2.90 +/- 0.13 nM). L-365,260 and PD-135,666 inhibited gastrin- and CCK-8-stimulated HDC activity with a high potency [50% inhibitory concentration (IC50) 1.00 +/- 0.08 and 4.2 +/- 0.7 nM for gastrin-stimulated and 1.95 +/- 0.21 and 1.78 +/- 0.12 nM for CCK-8-stimulated HDC activity, respectively], whereas L-364,718 was 50 to 100 times less potent (EC50 100 +/- 2.5 and 91.2 +/- 3.1 nM, respectively on gastrin- and CCK-8-stimulated HDC activity). Carbachol also dose-dependently increased HDC activity (EC50 7.08 +/- 0.32 nM), and its effect was reversed by selective muscarinic-receptor antagonists with the following order of potency: pirenzepine (IC50 15.1 +/- 1.2 nM) > para-fluoro-hexahydro-siladifenidol (IC50 0.316 +/- 0.02 microM) > 11-2[(2-[(diethyl-amino)-methyl]-1-piperidinyl)acetyl]-5,11-dihydro-6H- pyrido[2,3-b][1,4]benzodiazepine-6-one (IC50 28.5 +/- 1.1 microM). Moreover, gastrin and carbachol were able to modify slightly but significantly both the Michaelis constant (Km) and the maximal velocity (Vmax) of HDC in the same way (18-20% reduction of the Km and 25-30% increase of the Vmax).(ABSTRACT TRUNCATED AT 250 WORDS)