bluuebunny/crossref_metadata_2025 huggingface dataset:
Differential regulation of intestinal amino-oligopeptidase gene expression in neonatal and adult rats
Authors: Cohen M. L. , Santiago N. A. , Zhu J. S. , Gray G. M.
Published: December 2017

Intestinal amino-oligopeptidase (AOP) is an essential brush-border hydrolytic enzyme required for the surface digestion of nutrient oligopeptides produced from luminal pancreatic protease action on dietary protein. There is an abrupt rise in AOP catalytic activity during postnatal rat development, but the mechanism has not been defined. AOP expression was examined in rats 11 to 60 days of age by measurement of AOP mRNA, catalytic activity, and total AOP protein (by quantitative rocket immunoassay). Specific catalytic activity began increasing at 18 days, achieved a maximum by 22 days (+125% over 11 days), and remained stable thereafter. A 1.1-kb AOP cDNA, generated by the polymerase chain reaction and used to quantify specific mRNA, identified a single 3.8-kb species at all ages on Northern blots. The abundance of beta-actin mRNA, which increased slightly (+40%), and 7S RNA, which did not change, was also measured as developmental controls. The AOP mRNA-to-7S RNA ratio increased dramatically (+410%) between 11 and 60 days of age. A comparable initial rise in AOP activity (+130%) and in its mRNA (+170%) was observed between 11 and 22 days, followed by a divergence of the two curves, with a marked relative excess of mRNA compared with catalytic activity in the 60-day-old adult. The ratio of catalytically active to total immunoreactive AOP protein was higher in 60-day-old adults compared with both 11- to 15-day-old preweaned (65% of 60-day value) and 22- to 30-day-old postweaned (61% of 60-day value) animals.(ABSTRACT TRUNCATED AT 250 WORDS)
A capacitative Ca2+ influx is required for sustained fluid secretion in sublingual mucous acini
Authors: Melvin J. E. , Koek L. , Zhang G. H.
Published: December 2017

The Ca2+ dependence of muscarinic-induced fluid and electrolyte secretion was studied using rat sublingual mucous gland preparations. During stimulation, secretions from vascularly perfused glands were totally inhibited when perfused with a Ca(2+)-free medium. Fluid secretion correlated with sustained losses of 42K+ and 36Cl- content and sustained increases in 22Na+ content and the intracellular free Ca2+ concentration ([Ca2+]i) in fura-2-loaded acini. The magnitudes of the initial agonist-induced changes in Na+, K+, and Cl- content and [Ca2+]i were unaltered in a Ca(2+)-free medium, whereas extracellular Ca2+ removal resulted in the recovery of these ions during the sustained phase to pre-stimulation levels. The recovery of Cl- content induced by Ca2+ depletion was totally blocked in the presence of bumetanide, an inhibitor of Na(+)-K(+)-2Cl- cotransport, while 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS), an inhibitor of anion exchange, did not influence Cl- recovery in a HCO(3-)-containing solution (25 mM NaHCO3, 5% CO2). The stimulated increase in [Ca2+]i was not inhibited by the addition of voltage-activated Ca2+ channel blockers (D 888, nifedipine, and diltiazem) or in a Na(+)-free medium. Studies using the quench of fura-2 by Mn2+ as an index of Ca2+ influx and thapsigargin, an inhibitor of microsomal Ca(2+)-ATPase, indicate that a capacitative Ca2+ entry pathway mediates Ca2+ entry during stimulation. The above data demonstrate that Ca2+ uptake, which is dependent on the refill status of the agonist-sensitive intracellular Ca2+ pool, is a prerequisite for sustained muscarinic-induced fluid and electrolyte secretion in the rat sublingual mucous gland.
Neutrophil-induced liver cell injury in endotoxin shock is a CD11b/CD18-dependent mechanism
Authors: Jaeschke H. , Farhood A. , Smith C. W.
Published: December 2017

To investigate the role of neutrophils (PMNs) and PMN-dependent adhesion molecules in the pathogenesis of liver injury in a model of endotoxin shock, male ICR mice received a dose of 700 mg/kg galactosamine and 100 micrograms/kg Salmonella abortus equi endotoxin. PMNs accumulated continuously in the liver, reaching values of 446 +/- 71 PMNs/50 high-power fields at 9 h (basal value 18 +/- 7). Plasma alanine aminotransferase activities as index of parenchymal cell injury did not change up to 5 h posttreatment (basal value 35 +/- 5 U/l) but increased to 1,950 +/- 460 U/l at 9 h. The formation of glutathione disulfide (GSSG) in plasma as an index of an extracellular oxidant stress also increased only at 9 h. Pretreatment of animals with monoclonal antibodies against the CD11b and CD18 subunits of the CD11/CD18 integrin family on the surface of the PMN reduced the number of PMNs in the liver by 50% and significantly attenuated liver injury and GSSG formation. An anti-CD11a and a nonbinding control antibody were ineffective. It is concluded that PMNs are actively involved in the pathogenesis of galactosamine and endotoxin shock and that at least in part the accumulation of PMNs, the subsequent oxidant stress, and the tissue injury in this model of experimental hepatitis are CD11b/CD18 (Mac-1) dependent.
Hepatic and ileal transport and effect on biliary secretion of norursocholic acid and its conjugates in rats
Authors: Lillienau J. , Hagey L. R. , Borgstrom B.
Published: December 2017

The enterohepatic circulation of norursocholic acid (nUC) and its glycine (nUCG) and taurine (nUCT) conjugates was investigated in the rat; cholic acid (C) was studied as control. The biliary recovery of intravenously infused 14C-labeled bile acids was high: nUC, 88%; nUCG, 80%; nUCT, 99%, and C, 90%. Biliary recovery after the same bile acids were infused intraduodenally was similar: nUC, 90%; nUCG, 66%; nUCT, 97%; and C, 99%. The two conjugated bile acids, nUCG and nUCT, were not biotransformed during intestinal or hepatic transport; nUC was also secreted largely unchanged, but approximately 10% was secreted as an unknown conjugate or sulfate; C was completely conjugated with taurine or glycine. To compare the rates of active ileal transport, biliary recovery was measured after an in situ ileal perfusion technique. The rate of absorption of nUC, nUCG, and nUCT was one-fourth to one-half that of cholyltaurine, which served as control. Competition experiments indicated that the same transport system was involved. When infused intravenously, nUC, nUCG, and nUCT induced far less biliary lipid secretion than an identical dose of C; the secretion of both phospholipid and cholesterol was decreased, cholesterol to a greater extent than phospholipid. It is concluded that nUC and its conjugates are well transported by the ileum, are efficiently secreted into bile without undergoing appreciable hepatic biotransformation, and induce bile flow as other hydrophilic bile acids, but in contrast to C induce little phospholipid and cholesterol secretion into bile.
Impaired alanine uptake by basolateral liver plasma membrane vesicles from rats consuming ethanol
Authors: Smith D. J. , Ploch S. A.
Published: December 2017

Chronic ethanol consumption reduces alanine transport by rat basolateral liver plasma membrane (blLPM) vesicles; however, the mechanism for this effect remains uncertain. It may be related to the ethanol-induced changes in blLPM fluidity and lipid composition; alternatively ethanol might reduce the number of transporters in the blLPM. To investigate the effect of blLPM fluidity and lipid composition on Na(+)-dependent alanine uptake these parameters were altered in vitro. Increasing the blLPM fluidity had no effect on Na(+)-dependent alanine uptake by blLPM vesicles or the activity of amino acid transport systems, A and ASC. Because ethanol is known to reduce the blLPM cholesterol content, the influence of altering blLPM cholesterol on alanine transport by these membranes was investigated next. Neither an increase nor a decrease of the cholesterol content of the blLPM altered Na(+)-dependent alanine uptake or the activity of system A or ASC. Finally, the influence of chronic ethanol consumption on the specific binding of [3H]alanine to blLPM was studied. The dissociation constant for alanine binding to blLPM from ethanol-fed rats and their pair-fed controls was similar (1.9 +/- 0.2 vs. 2.0 +/- 0.3 mM); however, the maximal binding capacity for alanine was significantly (P less than 0.05) lower in the blLPM from ethanol-fed rats (316 +/- 53 pmol/mg protein) compared with their pair-fed controls (527 +/- 79 pmol/mg protein). These studies do not support the hypothesis that ethanol-induced changes in blLPM fluidity are responsible for the impaired alanine transport; they do suggest that ethanol may reduce the
D2O as a substitute for 3H2O, as a reference indicator in liver multiple-indicator dilution studies
Authors: Pang K. S. , Xu N. , Goresky C. A.
Published: December 2017

The hepatic space of distribution and the processes underlying uptake of tracer substrate may be appraised by the multiple-indicator dilution technique after simultaneous injection of noneliminated vascular (51Cr-labeled red blood cells), extracellular 125I-labeled albumin and [14C]sucrose (or [58Co]EDTA) as high- and low-molecular-weight interstitial references, respectively], and cellular (3H2O or [14C]urea) indicators, together with the tracer-labeled substrate. The use of 3H2O or [14C]urea, with [14C]- or [3H]sucrose, however, precludes the simultaneous introduction and analysis of the behavior of 3H- and 14C-labeled substrate and metabolite. An assay for the quantitation of D2O in plasma by Fourier transform infrared spectrometry was therefore developed such that D2O could be used in lieu of 3H2O in multiple-indicator dilution studies in the blood-perfused rat liver. In experiments performed with an injection dose containing 51Cr-labeled red blood cells, 125I-labeled albumin, [14C]sucrose, 3H2O, and D2O, D2O was found to behave virtually identical to 3H2O in blood and liver; the accessible cellular water spaces were 0.625 and 0.621 ml/g liver for 3H2O and D2O, respectively, and the corresponding ratios of the sum of the cellular water plus the interstitial water space to the sinusoidal water space were 3.87 and 3.89. D2O was found to be an ideal substitute and is much superior to [14C]urea, which exhibits a small red blood cell carriage effect and which is slightly less dispersed than 3H2O.
Pancreastatin inhibits pancreatic enzyme secretion by presynaptic modulation of acetylcholine release
Authors: Herzig K. H. , Louie D. S. , Tatemoto K. , Chung O. Y.
Published: December 2017

Pancreastatin (PST), a 49-amino acid polypeptide, inhibits endocrine and exocrine pancreatic functions. In this study, we examined the mechanism of the inhibitory action of PST on exocrine pancreatic secretion in the rat. In anesthetized rats prepared with pancreatic fistulas, intravenous administration of PST (500 pM.kg-1.h-1) completely inhibited 2-deoxyglucose (75 mg/kg)-stimulated amylase output to below basal levels. Because 2-deoxyglucose acts to stimulate the vagus, we assessed the ability of PST to inhibit carbachol-stimulated amylase release from isolated rat pancreatic acini. PST suppressed neither carbachol- nor cholecystokinin-stimulated amylase release, indicating that PST inhibits exocrine secretion via indirect mechanisms. To examine neural pathways for inhibition, we used pancreatic lobules to examine the action of PST on intrapancreatic neurons. Incubation of pancreatic lobules in 75 mM potassium buffer stimulated amylase release by a cholinergic pathway. PST dose dependently inhibited potassium-evoked amylase release, with maximal inhibition of 49.6 +/- 11%. In addition, when lobules were incubated with [3H]choline, PST inhibited KCl-stimulated release of synthesized [3H]acetylcholine by 43 +/- 5.7%. Other studies demonstrate that PST inhibits rat pancreatic enzyme secretion via presynaptic modulation of acetylcholine release.
Pharmacological characterization of histamine H3 receptors in isolated rabbit gastric glands
Authors: Bado A. , Moizo L. , Laigneau J. P. , Lewin M. J.
Published: December 2017

The effects of the specific H3 agonist (R)-alpha-methylhistamine (alpha-MeHA) and the specific H3 antagonist thioperamide were examined on histamine release and acid secretion [( 14C]-aminopyrine (AP) accumulation) by isolated rabbit gastric glands. Thioperamide significantly enhanced basal histamine release from the glands (+50% at 30 min for 10(-7) M thioperamide; P less than 0.01), and this increase was prevented by alpha-MeHA. Histamine-elicited AP accumulation was increased by 18% (P less than 0.05) by 10(-7) M thioperamide and decreased by 70% (P less than 0.01) by 10(-6) M of the H2 antagonist ranitidine. Thioperamide alone significantly enhanced AP accumulation in a dose-dependent manner, whereas alpha-MeHA had no effect of its own on this accumulation. Thioperamide stimulation of basal AP accumulation was not modified by ranitidine but was 50% decreased by alpha-MeHA. Furthermore, carbachol-induced AP accumulation was decreased by alpha-MeHA and increased by thioperamide; the latter effect was not blocked by ranitidine. These findings support that H3 receptors pharmacologically distinct from H2 receptors are involved in the regulation of histamine-stimulated acid secretion. They further suggest that these gastric H3 receptors occur in the gastric glands as 1) H3 autoreceptors located on the histamine-secreting cells and acting to downregulate histamine release from these cells and 2) H3 (or H3-like) receptors located on the parietal cell and regulating in a negative manner the acid secretory process.
Intrinsic factor receptor activity and cobalamin transport in bile duct-ligated rats
Authors: Seetharam S. , Ramanujam K. S. , Seetharam B.
Published: December 2017

The intrinsic factor (IF)-cobalamin (Cbl) receptor activity in the mucosal homogenates progressively decreased after bile duct ligation in the rat, and 80% of the receptor activity was decreased in 96 h after ligation. The activity was restored to normal values of 5.5-6 pmol of IF-[57Co]Cbl bound/g mucosa when the assays were performed with both conjugated and unconjugated bile acids. When [57Co]Cbl bound to intrinsic factor was orally administered, the tissue levels of [57Co]Cbl were decreased by 75-80% in bile duct-ligated rats. The apical membrane receptor activity was also decreased after bile duct ligation; however, the activity was stimulated twofold by the addition of ileal cytosol and threefold with the addition of both ileal cytosol and taurocholate (1 mM). Enhanced binding of IF-[57Co]Cbl to the apical ileal brush-border membrane occurred with the use of dialyzed ileal cytosol but not with cytosol isolated from duodenal or proximal jejunal mucosa. The enhanced binding obtained with ileal cytosol was abolished after its treatment with trypsin. These results suggest that luminal bile acids optimize the binding of IF-Cbl by the ileal membrane receptor via interactions with a cytosolic factor and thus influence the gastrointestinal absorption of cobalamin.
Vagal influence on colonic motor activity in conscious nonhuman primates
Authors: Dapoigny M. , Cowles V. E. , Zhu Y. R. , Condon R. E.
Published: December 2017

We investigated the role of the vagi in modulation of colonic motor activity in the fasted and fed states and determined the extent of vagal influence on colon motility in conscious monkeys. Monkeys were implanted with force transducers on the colon. A vagal cooling chamber was implanted supradiaphragmatically, and a vagal stimulating electrode was implanted just distal to the chamber. One week was allowed for recovery. After an overnight fast, control recordings were made for 1 h, and then the monkeys were either fed or remained fasting, with or without adrenergic blockade (propranolol and phentolamine). Then while recordings continued the vagi were cooled to their predetermined denervation temperature for 1 h. In a second set of experiments, adrenergic blockers were injected, and the vagi were stimulated during vagal cooling with or without atropine administration. In both the fasted and fed states, the contractile frequency was decreased during vagal cooling, with or without adrenergic blockade. With adrenergic blockade, however, the frequency of colon contractions was greater during cooling than during cooling without such blockade. Inhibition of colonic contractions during cooling decreased in magnitude from the proximal to the distal colon. Vagal efferent stimulation increased contractile frequency at all sites, but after atropine it decreased contractile frequency. We conclude that the vagi have either a direct or indirect influence on fasting and fed colonic motor activity throughout the colon, and that a nonadrenergic, noncholinergic inhibitory pathway is under vagal control.
Localization and characterization of pancreatic polypeptide receptors in rat adrenal glands
Authors: Whitcomb D. C. , Vigna S. R. , McVey D. C. , Taylor I. L.
Published: December 2017

Pancreatic polypeptide (PP) is released from pancreatic islets after meals or in response to stress. Although PP exhibits a wide spectrum of biological effects, few, if any, are mediated by a direct action of PP on its ultimate target organ. Recently, PP receptors have been identified in areas of the brain with an incomplete blood-brain barrier suggesting that PP may act indirectly through the central nervous system. In the present study, we sought to identify peripheral PP binding sites using an in vivo radioreceptor assay and in vitro autoradiography. Using these techniques, we have identified saturable binding sites for PP in the zona fasciculata, zona reticularis, and the medulla of the rat adrenal gland. We have characterized these sites using equilibrium analysis of membrane-radioligand binding and by quantitative autoradiography of radioligand binding to frozen tissue sections. Binding of PP to these sites is saturable, of high affinity, and specific as well as time, temperature, and membrane dependent. Moreover, PP binds to these putative receptor sites in vivo at physiological concentrations. Many of the actions of PPs have been demonstrated to be indirect. Because PP receptors have been identified in the brain and now in the adrenal gland, we suggest that some of the effects of PP may be mediated through direct and indirect modulation of the brain and adrenal axis.
Mechanisms of airway protection and upper esophageal sphincter opening during belching
Authors: Shaker R. , Ren J. , Kern M. , Dodds W. J. , Hogan W. J. , Li Q.
Published: December 2017

The mechanisms of airway protection, upper esophageal sphincter (UES) opening, and their coordination during belching were studied with a concurrent videoendoscopic, videofluoroscopic, and manometric technique. Analysis of videoendoscopic recordings revealed that glottal function during gastric and esophageal belching was similar and consisted of vocal cord adduction resulting in closure of intoitus to trachea, followed by anterior-caudad movement of the glottis, followed by slitlike or triangular UES opening. When a belch episode was associated with an intragastric pressure increase, in addition to the above features, there was approximation of arytenoids to the base of the epiglottis before the UES opened. Duration of vocal cord closure during belches induced by 40 ml intraesophageal air injection was significantly longer than belches induced by 20 ml (P less than 0.01). Vocal cord closure preceded the UES opening invariably. Analysis of videofluoroscopic recordings showed that hyoid bone movement during belching had a distinctive pattern different from its movement during swallowing. UES opening started generally when the hyoid bone was pulled anteriorly. Anterior hyoid excursion of 0.78 +/- 0.1 cm during belching was significantly shorter than its excursion of 1.8 +/- 0.09 cm during swallowing (P less than 0.01). We conclude that glottal closure is an integral component of both esophageal and gastric belch reflexes that prevents aspiration of regurgitated material into the airway. Glottal closure mechanism during belching has two tiers of closure: 1) vocal cord closure and 2) aryepiglottic approximation. Glottal and UES functions are closely coordinated during belching, and finally, during belching, UES is pulled open after its relaxation.
Hormones increase oxygen uptake in periportal and pericentral regions of the liver lobule
Authors: Matsumura T. , Yoshihara H. , Jeffs R. , Takei Y. , Nukina S. , Hijioka T. , Evans R. K. , Kauffman F. C. , Thurman R. G.
Published: December 2017

The effect of several hormones known to alter intracellular free Ca2+ on rates of O2 uptake in periportal and pericentral regions of the liver lobule was studied in the perfused liver. Regional O2 uptake was measured by stopping the flow and monitoring the decrease in O2 concentration. When perfusion was in the anterograde direction, basal rates of O2 uptake were two to three times higher in periportal than in pericentral regions, and phosphorylase alpha activity, which increases as a function of intracellular free Ca2+ levels, was higher in periportal regions. In contrast, when perfusion was in the retrograde direction, rates of O2 uptake were two to three times greater in pericentral regions. Infusion of epinephrine (0.1 microM) or angiotensin II (5 nM) increased the rate of O2 uptake nearly exclusively in downstream areas of the lobule where O2 tension was low. When perfusions were in the anterograde direction, epinephrine increased phosphorylase alpha activity significantly only in pericentral regions. Stimulation of O2 uptake by epinephrine was blocked by the alpha-adrenergic receptor blocker phentolamine (1 microM) but not by the beta-receptor blocker propranolol. Thus hormones that increase intracellular calcium stimulate O2 uptake predominantly in regions of the liver lobule where O2 tension is lowest, supporting the hypothesis that oxygen tension regulates O2 uptake in the liver via mechanisms involving intracellular free Ca2+.
Action profiles of nitric oxide, S-nitroso-L-cysteine, SNP, and NANC responses in opossum lower esophageal sphincter
Authors: Knudsen M. A. , Svane D. , Tottrup A.
Published: December 2017

Circular muscle strips from opossum lower esophageal sphincter were suspended in organ baths for measurement of isometric tension. Nonadrenergic noncholinergic (NANC) inhibitory nerves were stimulated by means of transmural field stimulation. This induced frequency-dependent relaxations of the muscle strips. Methylene blue (3 x 10(-6) M; inhibits guanylate cyclase) and pyrogallol (10(-4) M; generates superoxide anions) had no influence on relaxations, whereas oxyhemoglobin [10(-5) M; binds nitric oxide (NO) and other nitroso compounds extracellularly] inhibited relaxations at all frequencies. NO concentration dependently relaxed the muscle strips. Pyrogallol (10(-4) M) and methylene blue (3 x 10(-6) M) inhibited and oxyhemoglobin (10(-5) M) nearly abolished relaxation induced by NO. S-nitroso-L-cysteine caused concentration-dependent relaxations of the muscle strips, which were inhibited by pyrogallol (10(-4) M), whereas methylene blue (3 x 10(-6) M) augmented the action of S-nitroso-L-cysteine. Methylene blue (3 x 10(-6) M) had no influence on the concentration-dependent relaxations caused by sodium nitroprusside (SNP). Oxyhemoglobin (10(-5) M), and to a lesser extent pyrogallol (10(-4) M), both inhibited the effects of SNP. The action profiles for S-nitroso-L-cysteine, NO, and SNP differed from the action profile for NANC nerve-mediated response. Although pyrogallol inhibited the effects of SNP, the action profile generally resembled the action profile for NANC responses more closely than did the profiles for S-nitroso-L-cysteine or NO. In conclusion, of the nitroso compounds studied, SNP most closely resembled the response to NANC nerve stimulation. Neither NO nor S-nitroso-L-cysteine individually mimicked the NANC response.
Regulation of hepatic glycogenolysis and vasoconstriction during antigen-induced anaphylaxis
Authors: Hines K. L. , Fisher R. A.
Published: December 2017

Effects of sensitizing antigen (ovalbumin) on various physiological and hepatic parameters were investigated in sensitized rats and isolated perfused livers derived from sensitized rats. Administration of ovalbumin (500 micrograms) to the portal venous circulation of sensitized but not nonsensitized rats resulted in a rapid and sustained decrease in systemic arterial pressure, characteristic of antigen-induced anaphylaxis, and pronounced increases in hepatic portal pressure and blood glucose concentration. These antigen-mediated alterations were similar to those observed in response to platelet-activating factor (PAF) (0.1 micrograms/kg) administration to rats and were inhibited significantly by specific PAF receptor antagonist WEB 2086 (250 micrograms/kg). Infusion of ovalbumin (3.8 micrograms/ml) into isolated perfused livers derived from sensitized rats resulted in significant increases in hepatic glucose output and portal pressure and decreases in oxygen consumption, as observed in response to PAF (0.28 nM) infusion into perfused livers. These hepatic responses to ovalbumin were antigen specific and were not observed in nonsensitized rat perfused livers. Hemodynamic and glycogenolytic responses to ovalbumin in perfused livers were inhibited significantly but less effectively than similar responses to PAF by infusion of WEB 2086 (500 nM) into livers. Coinfusion of indomethacin (2.8 microM) and nordihydroguariatic acid (1 microM) with WEB 2086 (500 nM) into perfused livers inhibited further hemodynamic but not glycogenolytic responses to ovalbumin. Infusion of nitric oxide (34 microM) into sensitized rat perfused livers prevented the hemodynamic and glycogenolytic responses to both ovalbumin and PAF. These observations provide evidence that hepatic glycogenolysis and vasoconstriction are stimulated during antigen-induced anaphylaxis and suggest that these responses are mediated in part by PAF.
Effect of octreotide on sphincter of Oddi and gallbladder motility in prairie dogs
Authors: Ahrendt S. A. , Ahrendt G. M. , Lillemoe K. D. , Pitt H. A.
Published: December 2017

Somatostatin and its synthetic analogue, octreotide, inhibit gallbladder emptying and cause gallstones. Whether octreotide-induced alterations in sphincter of Oddi motility contribute to this process is unknown. We, therefore, examined the effect of octreotide on fasting and protein-stimulated sphincter of Oddi motility. In 25 anesthetized prairie dogs, sphincter of Oddi motility and gallbladder pressure were monitored during the intravenous administration of octreotide, cholecystokinin (CCK) octapeptide, atropine, the intraduodenal administration of casein, and combinations of these agents. Intravenous octreotide decreased fasting sphincter of Oddi motility index both with (59 +/- 19 vs. 84 +/- 28, P less than 0.05) and without (137 +/- 31 vs. 227 +/- 42, P less than 0.05) prior cholinergic blockade with atropine. Octreotide also prevented the increases in sphincter of Oddi motility and gallbladder pressure seen with intraduodenal casein. Exogenous CCK increased sphincter of Oddi motility index and gallbladder pressure despite the simultaneous administration of octreotide alone (357 +/- 109 vs. 137 +/- 31, P less than 0.07, and 11.2 +/- 1.0 mmHg vs. 9.6 +/- 0.6 mmHg, P less than 0.05) or the combination of octreotide and atropine (317 +/- 69 vs. 59 +/- 19, P less than 0.05, and 10.1 +/- 1.6 mmHg vs. 8.5 +/- 1.4 mmHg, P less than 0.05). We conclude that both a cholinergic and an octreotide-sensitive noncholinergic pathway stimulate fasting sphincter of Oddi motility in the prairie dog.
Both CCK-A and CCK-B/gastrin receptors mediate pepsinogen release in guinea pig gastric glands
Authors: Lin C. W. , Bianchi B. R. , Miller T. R. , Witte D. G. , Wolfram C. A.
Published: December 2017

We evaluated the affinity of cholecystokinin octapeptide (CCK-8), gastrin, and subtype-selective CCK agonists for CCK/gastrin receptors and compared it with the ability of these peptides to stimulate phosphoinositide (PI) hydrolysis and pepsinogen release in guinea pig gastric glands. Competitive binding studies using 125I-labeled Bolton-Hunter-CCK-8 and 125I-gastrin showed the presence of CCK-B/gastrin receptors in gastric glands and dispersed chief cells. In contrast, the potency of peptides in stimulating PI hydrolysis in both gastric glands and dispersed chief cells displayed a profile similar to CCK-A receptors found in pancreatic acini, i.e., CCK-8 = A 71378 greater than A 71623 greater than A 70874 much greater than A 72962 = CCK-8 (desulfated) greater than gastrin II greater than gastrin I. In general, the rank order of potency of peptides for stimulation of PI hydrolysis correlated well with their ability to stimulate pepsinogen release. At concentrations greater than 10 microM, efficacies of gastrin I and II in stimulating pepsinogen release from gastric glands were near 90% of the maximal activity of CCK-8. The inhibitory potency of MK-329, a selective CCK-A receptor antagonist, was similar against either CCK-8 (10 nM) or gastrin I (10 microM), except that a minor portion (approximately 30-40%) of gastrin I-induced pepsinogen release was insensitive to MK-329. The MK-329-insensitive component was inhibited by CI-988, a potent and selective CCK-B/gastrin receptor antagonist.(ABSTRACT TRUNCATED AT 250 WORDS)
Renal failure increases gastric mucosal blood flow and acid secretion in rats: role of endothelium-derived nitric oxide
Authors: Quintero E. , Guth P. H.
Published: December 2017

Because of the contradictory findings in clinical studies, and the complete lack of animal studies, the purpose of this investigation was to characterize the changes in gastric mucosal blood flow (GMBF) and acid secretion in an animal model of chronic renal failure. Rats with chronic renal failure induced by partial kidney infarction had a significantly higher basal GMBF and lower gastric vascular resistance than control rats. The gastric acid secretory and mucosal hyperemic response to pentagastrin were markedly enhanced in renal failure rats. Because endothelial-derived nitric oxide (NO) is an endogenous vasodilator that regulates gastric vascular tone, we hypothesized that NO mediates the gastric hyperemia of renal failure rats. The administration of N omega-nitro-L-arginine methyl ester (L-NAME), a specific inhibitor of NO formation, produced a significantly greater decrease in GMBF in renal failure rats than in control rats, including a low dose inhibiting the basal hyperemia in renal failure rats but having no effect in control rats. It also attenuated pentagastrin-stimulated GMBF in both groups. In contrast, L-NAME produced a similar decrease in basal skeletal muscle blood flow in both renal failure and control rats. We conclude that in the renal failure rat 1) there is an increased basal GMBF and pentagastrin-stimulated acid output and GMBF, and 2) this gastric mucosal hyperemia is mediated by NO.
Polyamines attenuate jejunal mucosal injury induced by oleic acid
Authors: Kvietys P. R. , Specian R. D. , Cepinskas G.
Published: December 2017

Effects of putrescine, spermidine, and spermine on lipid-induced injury to jejunal mucosa were assessed in anesthetized rats. Mucosal epithelial integrity was continuously monitored by measuring blood-to-lumen clearance of 51Cr-labeled EDTA. Perfusion of jejunal lumen with emulsified lipid (20 mM sodium taurocholate and 40 mM oleic acid) increased 51Cr-EDTA clearance. Addition of spermidine (0.5 mM), but not putrescine (2.0 mM) or spermine (0.25 mM), to the lipid perfusate reduced the increment in 51Cr-EDTA clearance. Histological evaluation of jejunal mucosa indicated that the epithelial lining of the villous tips was damaged by emulsified oleic acid and that this injury was ameliorated by spermidine. Pretreatment of jejunal mucosa with spermidine did not prevent disruption of mucosal integrity induced by a subsequent perfusion with emulsified lipids. Intravenous infusion of spermidine to achieve an extracellular concentration of 0.5 mM did not prevent the lipid-induced increase in 51Cr-EDTA. Spermidine also ameliorated lipid-induced disruption of Caco-2 cell monolayers in culture; this protective effect was dose dependent and was observed only when spermidine was applied to the apical aspect of the monolayers. These findings indicate that spermidine must be present on the apical portion of the epithelial cell during lipid insult. Substitution of lysine or arginine for spermidine did not reduce the extent of lipid-induced injury to jejunal mucosa, indicating that spermidine's protective effects cannot simply be attributed to its cationic nature. Spermidine did not alter the turbidity of a micellar oleic acid solution, indicating that spermidine was not removing oleic acid from the soluble phase.(ABSTRACT TRUNCATED AT 250 WORDS)
Bile salt hydrophobicity controls vesicle secretion rates and transformations in native bile
Authors: Cohen D. E. , Leighton L. S. , Carey M. C.
Published: December 2017

After drainage of the bile salt pool, we infused unanesthetized bile fistula prairie dogs (Cynomys ludovicianus) intravenously with taurine-conjugated chenodeoxycholate (TCDC), cholate (TC), ursodeoxycholate (TUDC), and ursocholate (TUC) in concentrations that attained greater than 94% enrichment of biliary bile salts. With decreases in bile salt hydrophobicity, maximum steady state lecithin and to a lesser extent cholesterol secretion rates decreased in the rank order, TCDC greater than TC greater than TUDC greater than TUC. By phase analysis, TCDC-rich and TC-rich biles plotted inside their respective micellar zones, whereas TUDC-rich and TUC-rich biles plotted outside and were so-called "supersaturated" with cholesterol. Quasi-elastic light scattering and electron microscopy, when performed within 30 min of collection, revealed unilamellar vesicles in all biles. By 24 h, vesicles in TCDC-rich and TC-rich biles had dissolved into mixed micelles, whereas vesicles in TUDC-rich biles formed mixed micelles plus multilamellar liquid crystals, and vesicles in TUC-rich biles formed multilamellar liquid crystals exclusively. Because cholesterol/phospholipid molar ratios of multilamellar liquid crystals were less than or equal to 1, cholesterol monohydrate crystals did not form in these biles. We conclude that, despite drastic alterations in bile salt detergency, unilamellar vesicles are the final common pathway for lecithin and cholesterol secretion into bile. During equilibration of bile, the fate of unilamellar vesicles may be micellar, micellar plus liquid crystalline, or liquid crystalline only depending on the detergency (i.e., hydrophobic-hydrophilic balance) of the secreted bile salt.
Pharmacology of portal-systemic collaterals in portal hypertensive rats: role of endothelium
Authors: Mosca P. , Lee F. Y. , Kaumann A. J. , Groszmann R. J.
Published: December 2017

The portal-systemic collateral circulation of portal hypertensive rats was studied. The collaterals were perfused through the mesenteric vein with Krebs solution, which was allowed to escape through the jugular veins. The portal-collateral resistance can be quantitated from slopes of the pressure-flow relationships. In collaterals perfused at constant flow, both norepinephrine (NE) and 5-hydroxytryptamine (5-HT) increased the perfusion pressure. Phentolamine caused surmountable antagonism of the constrictor effects of NE, suggesting an involvement of alpha-adrenoceptors. The effects of 5-HT were competitively blocked by the 5-HT2 receptor-selective antagonist ICI 169,369. Isoproterenol dilated NE-preconstricted collaterals. The effect of isoproterenol was blocked by propranolol, demonstrating that the effect was mediated by beta-adrenoceptors. Acetylcholine (ACh) dilated NE-preconstricted collaterals. The dilatation effect of ACh was absent in collaterals in which the endothelium was removed. The competitive inhibitor of the nitric oxide synthase, N omega-nitro-L-arginine (L-NNA), increased collateral resistance and prevented the ACh-induced dilatation of the collaterals. The constrictor response to L-NNA and the blockade of the ACh-induced relaxation by both L-NNA and removal of endothelium are consistent with an involvement of nitric oxide. This experimental model can thus be used to explore the pathophysiological and the pharmacological properties of the collateral venous bed in portal hypertensive states.
Novel sites for expression of an Escherichia coli heat-stable enterotoxin receptor in the developing rat
Authors: Laney D. W. , Mann E. A. , Dellon S. C. , Perkins D. R. , Giannella R. A. , Cohen M. B.
Published: December 2017

Escherichia coli heat-stable enterotoxin (STa) mediates diarrheal disease by binding to and activating an intestinal transmembrane receptor, guanylate cyclase C (GC-C). To test the hypotheses that there was 1) increased perinatal expression of GC-C in rat intestine and 2) GC-C expression and STa binding in extraintestinal tissues of immature rat, we prepared whole cell membranes and total RNA from jejunum, ileum, colon, liver, kidney, heart, lung, brain, testis, and placenta of rats ranging in age from 12 days gestation to adult. Northern analysis demonstrated the presence of a unique 3.8-kb mRNA transcript at all ages in the jejunum, ileum, colon, and, to a lesser degree, in the testis. GC-C was also detected by Northern analysis in liver (from gestational age 18 days through 14 days postnatal) and in placenta. Steady-state mRNA encoding GC-C was not detected by Northern analysis in the other organs examined. GC-C-specific mRNA expression was greatest in the perinatal period in the jejunum, ileum, and liver. Specific binding of 125I-labeled STa was found in each of the tissue membranes in which GC-C mRNA was present; binding was not present in those tissues that had no detectable GC-C mRNA. The existence of GC-C in extraintestinal organs in the rat, and the development changes in GC-C expression support our hypothesis that GC-C, apart from its role as an STa receptor in mediating diarrheal disease, also serves as a receptor for an endogenous ligand.
Characterization of H2 histamine receptor: linkage to both adenylate cyclase and [Ca2+]i signaling systems
Authors: Delvalle J. , Wang L. , Gantz I. , Yamada T.
Published: December 2017

We undertook these studies to examine the intracellular mechanisms of histamine action using a rat hepatoma-derived cell line that had been transfected to express the H2 histamine receptor cDNA. Transfected cells demonstrated increased adenosine 3',5'-cyclic monophosphate production, membrane inositol phospholipid turnover, and intracellular Ca2+ concentration ([Ca2+]i) in response to histamine. All of the effects could be inhibited with the H2 histamine receptor antagonist cimetidine, and the increased membrane inositol phospholipid turnover and [Ca2+]i were abolished by cholera toxin pretreatment of cells. These data support the notion that a single histamine H2 receptor can be linked to two stimulatory intracellular signaling systems.
Lipocytes from fibrotic rat liver have an impaired feedback response to procollagen propeptides
Authors: Ikeda H. , Wu G. Y. , Wu C. H.
Published: December 2017

Procollagen propeptides have been previously shown to be taken up by cultured fibroblasts and to inhibit collagen production at translational and transcriptional levels. In hepatic fibrosis, Ito cells are thought to be major contributors to collagen overproduction. We wondered whether an impaired response to procollagen propeptides by Ito cells from fibrotic liver could be a mechanism involved in collagen overproduction in hepatic fibrosis. In the presence of type I procollagen carboxy-terminal propeptide (200 nM), collagen production by Ito cells from normal rats was significantly decreased to 62.0% of control, whereas collagen production by Ito cells from two models of hepatic fibrosis in the rat, bile duct ligation and carbon tetrachloride treatment, was not significantly changed (102.4 and 102.6% of controls, respectively). By measurement of type I procollagen mRNA levels, this difference in response to procollagen carboxy-terminal propeptide was determined to occur at a pretranslational level. The rates of uptake, transfer to the nuclear compartment, and degradation of procollagen propeptide were not significantly different in Ito cells from normal and fibrotic liver.
Regulation of secretion of pancreatic spasmolytic polypeptide from porcine pancreas
Authors: Rasmussen T. N. , Harling H. , Thim L. , Pierzynowski S. , Westrom B. R. , Holst J. J.
Published: December 2017

We studied the neural and hormonal regulation of the secretion of pancreatic spasmolytic polypeptide (PSP), a potential growth factor, from isolated perfused porcine pancreas and the pancreatic exocrine secretion of PSP in response to a meal in young conscious pigs. PSP concentrations in the pancreatic juice ranged from 1 to 180 micrograms/ml. PSP released to the venous effluent amounted to 0.4-7% of the total output. Thus PSP is predominantly an exocrine product. Electrical vagal nerve stimulation increased PSP output 30-fold. Acetylcholine mimicked the effect of nerve stimulation, which was inhibited but not abolished by atropine. Both vasoactive intestinal polypeptide and gastrin-releasing peptide stimulated PSP secretion. PSP concentration in the juice decreased in response to secretin and increased after cholecystokinin octapeptide (CCK-8), but both increased PSP output. In conscious pigs, pancreatic secretion of protein and PSP increased in parallel. Like pancreatic enzyme secretion, we conclude that PSP secretion is controlled by parasympathetic mechanisms that include both cholinergic and peptidergic pathways and by endocrine mechanisms that may include both secretin and CCK-8.
Selective accumulation of methylene blue by interstitial cells of Cajal in canine colon
Authors: Liu L. W. , Thuneberg L. , Daniel E. E. , Huizinga J. D.
Published: December 2017

The network of interstitial cells of Cajal (ICC) at the submucosal surface of the canine colon was selectively stained by incubation with 15-50 microM methylene blue for 30-45 min. The network was composed of regularly scattered ICC cell bodies interconnected by long processes. Circular muscle cells were unstained. Staining of neurons was limited to one or two axons within bundles. The ICC network had a thickness of a single cell, since no overlapping of ICC cell bodies was observed. The ICC network connected the circular muscle cells at the submucosal surface across the septa which circumferentially divided the circular muscle into lamellae. Methylene blue at 50 microM slightly decreased the resting membrane potential and increased the duration of slow waves, leading to an increase in the force of phasic contractions, with no significant influence on other slow-wave parameters. Methylene blue produced neither electrophysiological nor mechanical effects on circular muscle preparations from which the submuscular ICC network was removed, indicating that the excitatory effects of methylene blue on the full-thickness circular muscle layer were mediated by ICC. In summary, the three-dimensional aspects of the submuscular ICC network can be visualized after selective staining by methylene blue. This staining does not affect physiological characteristics of smooth muscle cells.
Mucosal stimulation evokes vasodilation in submucosal arterioles by neuronal and nonneuronal mechanisms
Authors: Vanner S. , Jiang M. M. , Surprenant A.
Published: December 2017

The effects of mechanical stimulation of intestinal mucosa on submucosal arterioles of guinea pig ileum were examined using video microscopy of in vitro preparations consisting of submucosal plexus with adjacently attached mucosa. Mucosal stimulation did not alter the diameter of relaxed vessels but dilated arterioles preconstricted with phenylephrine or the prostaglandin analogue U-46619. Tetrodotoxin (TTX) or muscarinic receptor antagonists inhibited the vasodilation evoked by mucosal stimulation in 60% of preparations examined from normal and extrinsically denervated animals. The TTX-sensitive vasodilation to mucosa stimulation was partially inhibited by the 5-hydroxytryptamine3 (5-HT3) receptor antagonist ICS 205930. The TTX-insensitive vasodilation was largely prevented when the histamine receptor antagonists cimetidine and pyrilamine and the prostaglandin synthesis inhibitor indomethacin were applied. This study has demonstrated a reflex vasodilation to mucosal stimulation in an isolated submucosal plexus preparation that involves both neuronal and nonneuronal pathways. The neuronal pathway converges on cholinergic vasodilator neurons in the submucosal ganglia. The nonneuronal pathway involves the release of 5-HT, histamine, and prostaglandins from mucosal elements; 5-HT excites cholinergic vasodilator neurons, whereas histamine and prostaglandins dilate submucosal arterioles directly.
Regulation of exocrine pancreatic secretion by cerebral TRH and CGRP: role of VIP, muscarinic, and adrenergic pathways
Authors: Messmer B. , Zimmerman F. G. , Lenz H. J.
Published: December 2017

The central nervous system effects of thyrotropin-releasing hormone (TRH) and calcitonin gene-related peptide (CGRP) on exocrine pancreatic secretion were studied in freely moving rats. TRH (0.05-0.5 nmol) significantly stimulated, whereas CGRP (0.1-1.0 nmol) significantly inhibited, volume, protein, and bicarbonate secretion. Pretreatment of the animals with the ganglionic blocking agent chlorisondamine abolished the pancreatic responses produced by both peptides. In contrast, vagotomy abolished the stimulatory effect of TRH, whereas noradrenergic blockade with bretylium or phentolamine abolished the inhibitory effect of CGRP. Atropine significantly attenuated, but the vasoactive intestinal peptide (VIP) antagonist [D-p-Cl-Phe6, Leu17]VIP completely abolished the stimulatory effect of TRH. Pancreatic secretory responses stimulated by cerebral TRH or by peripheral VIP were inhibited dose dependently by peripheral [D-p-Cl-Phe6,Leu17]VIP. Inhibition of pancreatic secretion induced by cerebral CGRP or by peripheral norepinephrine was prevented by intravenous phentolamine. These results indicate 1) cerebral TRH stimulates and cerebral CGRP inhibits exocrine pancreatic secretion in freely moving rats; 2) the effects of TRH are mediated by vagal efferents, and the primary peripheral transmitter appears to be VIP acting on VIP receptors, whereas muscarinic efferents are less important; and 3) the effects of CGRP are mediated by sympathetic noradrenergic efferents via alpha-adrenergic receptors.
Bile salts and ileal calcium transport in rats: a neglected factor in intestinal calcium absorption
Authors: Hu M. S. , Kayne L. H. , Willsey P. A. , Koteva A. B. , Jamgotchian N. , Lee D. B.
Published: December 2017

Ileum displays little active transcellular calcium (Ca2+) absorption but is credited with the bulk of Ca2+ absorbed in vivo. We examined the effect of taurodeoxycholic acid (TDC, 2 mM), a bile salt, on mannitol (MN, a marker of intercellular solute traffic) and Ca2+ fluxes in rat ileum. In the absence of electrochemical gradients between the mucosal (M) and serosal (S) bathing media in an Ussing chamber, net flux (Jnet) was observed in the S-to-M direction for both MN and Ca2+, i.e., the unidirectional secretory S-to-M flux (Js-->m) exceeded the absorptive M-to-S flux (Jm-->s). Mucosal TDC caused simultaneous increase in transepithelial conductance and Js-->m for both MN and Ca2+. This was followed by even greater increases in MN and Ca2+ Jm-->s, so that ultimately Jm-->s equaled Js-->m in each case. In control tissue, Js-->m for Ca2+ appeared to permeate exclusively through the intercellular MN pathway while part of Jm-->s for Ca2+ appeared to traverse through a non-MN route. After the TDC-induced increase in intercellular solute permeability, both Ca2+ fluxes appeared to traverse through the aqueous MN conduit. During the postprandial state, the presence of bile salts and the relative abundance of Ca2+ in ileal lumen can cause bulk Ca2+ absorption through the intercellular pathway.