bluuebunny/crossref_metadata_2025 huggingface dataset:
Detection of nitric oxide production and its role in pancreatic ischemia-reperfusion in rats
Authors: Tanaka S. , Kamiike W. , Kosaka H. , Ito T. , Kumura E. , Shiga T. , Matsuda H.
Published: December 2017

Partial ischemia of rat pancreas body and tail was obtained by occlusion of the celiac axis for 1 h after gastrectomy. The plasma level of nitrite plus nitrate in both systemic and portal venous blood after reperfusion was significantly higher than that after sham operation and ischemia alone. The elevation after reperfusion was significantly decreased by NG-nitro-L-arginine methyl ester (L-NAME). Simultaneous administration of L-arginine counteracted the L-NAME-induced decrease in the level of nitric oxide (NO) end products. Generation of NO was further demonstrated by nitrosylhemoglobin detection by electron spin resonance in the blood after reperfusion. On the other hand, the plasma level of lipase, a marker of damage to pancreatic exocrine tissue, was significantly increased after ischemia-reperfusion and further increased by administration of L-NAME. This increase in lipase correlated with a decrease in tissue blood flow in the pancreas. These results suggest that NO is generated during and may have a protective role in ischemia-reperfusion of the rat pancreas.
Roles of ET-1 in endotoxin-induced microcirculatory disturbance in rat small intestine
Authors: Miura S. , Fukumura D. , Kurose I. , Higuchi H. , Kimura H. , Tsuzuki Y. , Shigematsu T. , Han J. Y. , Tsuchiya M. , Ishii H.
Published: December 2017

The major objective of this study was to investigate whether endothelin-1 (ET-1) plays a significant role in endotoxin-induced microcirculatory disturbances of the intestinal mucosa. Submucosal microvessels of the rat ileum were observed by intravital microscopy with a high-speed video camera system. Preceding the apparent intestinal mucosal damage, red blood cell (RBC) velocity was significantly decreased 30 min after endotoxin treatment in both arterioles and venules. The number of leukocytes sticking to submucosal venules was significantly increased at 30 min. BQ-123, an ETA-receptor antagonist, significantly attenuated the decrease in RBC velocity and also prevented an increase in leukocyte sticking as well as the subsequent mucosal damage induced by endotoxin. The ET-1 concentrations began to be elevated in plasma at 15 min and in the mucosa at 30 min and subsequently further increased in a time-dependent manner. A significant decrease in calcium-dependent nitric oxide synthase activity and significant increases in the concentration of platelet-activating factor (PAF) were demonstrated in the intestinal mucosa after endotoxin treatment. BQ-123 also significantly attenuated these changes. We concluded that the increased ET-1 production in intestinal mucosa induced by endotoxin stimulation could lead to leukocyte sticking and decreased RBC velocity in the intestinal microcirculatory beds via ETA receptors, which are closely related to increased production of PAF and decreased synthesis of constitutive nitric oxide.
Intestinal distribution of human Na+/H+ exchanger isoforms NHE-1, NHE-2, and NHE-3 mRNA
Authors: Dudeja P. K. , Rao D. D. , Syed I. , Joshi V. , Dahdal R. Y. , Gardner C. , Risk M. C. , Schmidt L. , Bavishi D. , Kim K. E. , Harig J. M. , Goldstein J. L. , Layden T. J. , Ramaswamy K.
Published: December 2017

The identity of Na+/H+ exchanger (NHE) isoforms in the human small intestine and colon and their role in vectorial Na+ absorption are not known. The present studies were undertaken to examine the regional and vertical axis distribution of NHE-1, NHE-2, and NHE-3 mRNA in the human intestine. Ribonuclease protection assays were used to quantitate the levels of mRNA of these isoforms in various regions of the human intestine. In situ hybridization technique was used to localize NHE-2 and NHE-3 mRNA in the colon. The NHE-1 isoform message was present uniformly throughout the length of the human intestine. In contrast, mRNA levels for human NHE-2 and NHE-3 isoforms demonstrated significant regional differences. The NHE-3 abundance was found in decreasing order: ileum > jejunum > proximal colon = distal colon. The NHE-2 message level in the distal colon was significantly higher than in the proximal colon but was evenly distributed in the small intestine. In addition, NHE-2 mRNA was present in surface epithelial cells as well as in cells of the crypt region, suggesting the presence of NHE-2 message throughout the vertical axis of the colonic crypts. In contrast, NHE-3 mRNA was localized to surface colonocytes in the proximal colon. On the basis of this tissue-specific localization of NHE-2 and NHE-3 mRNA, it can be speculated that the relative contribution of NHE-2 and NHE-3 isoforms in Na+ absorption in the human intestine may be region specific, and these putative apical isoforms may be differentially regulated.
A low-protein diet ameliorates disrupted diurnal locomotor activity in rats after portacaval anastomosis
Authors: Steindl P. E. , Coy D. L. , Finn B. , Zee P. C. , Blei A. T.
Published: December 2017

In previous studies we noted a disruption of the circadian locomotor activity rhythm in rats after portacaval anastomosis (PCA). To examine whether this abnormality is related to factors that aggravate hepatic encephalopathy in humans, we studied the effect of dietary formulation and protein content on body weight, locomotor activity, and entrainment to the light-dark cycle in rats after PCA or sham operation. Postoperative weight loss was prevented by pair-feeding with a purified liquid diet. However, the behavioral abnormalities persisted in PCA rats fed a high-protein diet, with a reduction in total activity and entrainment to the light-dark cycle. These were ameliorated by a low dietary protein content. Since this treatment reduces the load of gut-derived nitrogenous substances that might alter brain metabolism, our data strengthen the hypothesis that the abnormal circadian activity patterns in PCA rats may be part of the spectrum of hepatic encephalopathy.
Dynamic aspects of glutathione and nitric oxide metabolism in endotoxemic rats
Authors: Minamiyama Y. , Takemura S. , Koyama K. , Yu H. , Miyamoto M. , Inoue M.
Published: December 2017

Glutathione is one of the most abundant thiols in mammalian tissues and plays important roles in the defense mechanism and detoxification of various metabolites, such as reactive xenobiotics and free radicals. Nitric oxide (NO) readily reacts with thiol compounds, thereby generating chemically stable S-nitrosothiols. Although endotoxin has been known to induce NO synthase in various organs, particularly liver and spleen, and enhances the production of NO, correlation between NO and glutathione metabolism in endotoxemic subjects remains to be elucidated. The present work examines the changes in NO and glutathione metabolism in endotoxemic rats. Administration of lipopolysaccharide (LPS) markedly decreased the glutathione levels in plasma and bile, whereas it decreased the hepatic level only slightly. NG-nitro-L-arginine (L-NNA), a NO synthase inhibitor, inhibited the LPS-induced decrease of glutathione in plasma and bile. Administration of LPS increased the biliary levels of gamma-glutamyl transpeptidase (gamma-GTP) without affecting its thiol levels. Acivicin, a gamma-GTP inhibitor, inhibited the LPS-induced decrease of glutathione in plasma and bile without affecting its hepatic levels. Analysis with the use of L-buthionine sulfoximine revealed that the turnover of hepatic glutathione significantly increased in LPS-treated rats by some L-NNA-inhibitable mechanism. These results suggest that endotoxin might enhance the NO production in the liver and other tissues and significantly modulate the interorgan metabolism of reduced glutathione.
Superior mesenteric artery blood flow and indomethacin-induced intestinal injury and inflammation
Authors: Battarbee H. D. , Grisham M. B. , Johnson G. G. , Zavecz J. H.
Published: December 2017

Intestinal injury caused by nonsteroidal anti-inflammatory drugs (NSAIDs) is associated with increased mucosal permeability, microvascular injury, focal intravascular thrombus formation, fibrin deposition, and neutrophil infiltration. Ulcerations and adhesions are also prominent feature of this injury. Although NSAID-induced inhibition of prostaglandin formation has been suggested to produce ischemic injury and inflammation, no studies have directly assessed intestinal blood flow in experimental NSAID-induced enteropathy. This study tested the hypothesis that indomethacin-induced small bowel injury and inflammation result from intestinal ischemia. With the use of pulsed Doppler flowmetry, superior mesenteric artery blood flow was continuously monitored in conscious rats after doses of indomethacin known to promote acute and then chronic small bowel inflammation (7.5 mg/kg, 2 sc doses spaced 24 h apart). After 72 h, rats were anesthetized and a section of small bowel was removed for histology and intestinal myeloperoxidase activity measurements. Mean arterial blood pressure was not affected until 32 h after indomethacin, when it decreased 20% (P < 0.05) to P < 0.01). Sustained blood flow changes first occurred at 20 h, when an increase of 15% (P < 0.01) was observed, whereas flow resistance decreased. Flow resistance continued to decrease for the remainder of the 72-h period, and there was an accompanying blood flow increase to +40% (P < 0.05 to P < 0.01). Intestinal ulcers developed in 86% of indomethacin-treated rats. Adhesions, dilation, and thickening of the distal jejunum and proximal ileum were observed in most indomethacin-treated rats. Histological grading of intestinal injury yielded scores of 7.1 +/- 1.2 and zero for indomethacin-treated and vehicle-injected rats, respectively (P < 0.01). Myeloperoxidase activity was greater in indomethacin-treated rats (6.7 +/- 1.9 vs. 1.8 +/- 0.3 U/cm, P < 0.05). These results suggest that indomethacin-induced enteropathy is associated with an increase, not a decrease, in superior mesenteric artery blood flow. Therefore, ischemia dose not appear to be a mechanism by which subcutaneous indomethacin administration produces small intestinal injury and inflammation.
Regulation and function of extracellular matrix intestinal epithelial restitution in vitro
Authors: Goke M. , Zuk A. , Podolsky D. K.
Published: December 2017

Repair of epithelial injury in the gastrointestinal tract is initially accomplished by migration of epithelial cells from the wound edge (“restitution”). To assess expression and function of the extracellular matrix (ECM) in the restitution phase after epithelial injury, in vitro studies using wounded monolayers or a rat intestinal epithelium-derived cell line (IEC-6) were undertaken. IEC-6 cells expressed fibronectin (FN) mRNA and protein in large amounts and lesser quantities of laminin-beta 1 (LN beta 1) and LN gamma 1. Collagen IV (Col IV) was weakly expressed, and LN alpha 1 was not detected. After wounding a significant decrease in FN, LN beta 1, LN gamma 1, and Col IV alpha 1 mRNA steady-state levels was observed; mean content 24 h after wounding was reduced by 75–90%. FN, LN, and Col IV proteins were also reduced. The downregulation of these ECM transcripts and proteins could be substantially prevented by transforming growth factor-beta 1, a restitution-promoting growth factor. In addition to changes of expression, the distribution of FN and LN was also altered in migrating cells after wounding, as assessed by immunofluorescence. Arg-Gly-Asp peptides that recognize the major cell attachment site on FN and antibodies recognizing the main noncollagenous domain of Col IV inhibited cell migration, but immunoneutralizing anti-LN antisera did not affect restitution. In conclusion, although paradoxically downregulated after wounding, ECM proteins, in particular FN and Col IV molecules, are able to enhance intestinal epithelial restitution.
ATP-dependent copper transporter, in the Golgi apparatus of rat hepatocytes, transports Cu(II) not Cu(I)
Authors: Bingham M. J. , Ong T. J. , Ingledew W. J. , McArdle H. J.
Published: December 2017

The Wilson disease adenosinetriphosphatase (ATPase; ATP7B) is believed to bind copper as Cu(I). We provide evidence to suggest that the ATPase actually transports Cu as Cu(II). When the copper is presented to rat liver microsomes as Cu(I), virtually all uptake is ATP independent. If the copper is presented as copper oxalate [Cu(II)], total uptake is reduced to approximately 10% of Cu(I) levels, but ATP-dependent uptake rises, both as a proportion of total uptake and in absolute terms. The reducing agent vitamin C and the Cu(I) chelator bathocuproine both override the effect of oxalate. The data indicate that there are two transporters in the microsomes, an ATP-independent Cu(I) transporter and an ATP-dependent Cu(II) pump. The activity of the Cu(I) transporter correlates most strongly with alkaline phosphatase, suggesting that it is derived from plasma membrane contamination. Cu(II) ATP-dependent transport correlates only with beta-1, 4-galactosyltransferase, which indicates that it is located in the Golgi apparatus.
Preservation of intestinal gene expression during hibernation
Authors: Carey Hannah V. , Martin Sandra L.
Published: December 2017

The role of luminal nutrients in regulating enterocyte gene expression was studied in a natural model for long-term fasting, the hibernating ground squirrel. Squirrels were studied during the active season and during the hibernation season when they had not eaten for at least 12 wk. The specific activities of sucrase, isomaltase, and intestinal alkaline phosphatase in jejunal brush-border membranes were similar in hibernating and active squirrels, whereas amino-oligopeptidase was reduced in hibernators. Na+-K+-adenosinetriphosphatase activity in jejunal mucosa was unchanged by hibernation. Densitometric analysis of Western blots showed that abundance of sucrase-isomaltase (SI), amino-oligopeptidase, and the Na+-glucose cotransporter SGLT1 was similar in the two activity states. Preservation of SI abundance in hibernation was confirmed by immunocytochemistry. Slot-blot analysis revealed no differences in mRNAlevels for these proteins between hibernating and active squirrels. Enterocyte proliferation and migration rates were greatly suppressed in torpid squirrels but increased immediately upon rewarming during arousals. These results demonstrate the striking constancy of enterocyte gene expression despite long-term fasting in a hibernating mammal.

small intestine; brush-border proteins; enzymes; sodium-glucose cotransporter

Submitted on November 15, 1995

Accepted on April 24, 1996
Electrophysiological characterization of a motilin agonist, GM611, on rabbit duodenal smooth muscle
Authors: Yamada K. , Chen S. , Abdullah N. A. , Tanaka M. , Ito Y. , Inoue R.
Published: December 2017

Effects of motilin and a newly synthesized erythromycin derivative, GM611, on membrane potential and currents of rabbit duodenal smooth muscle have been investigated by intracellular potential recording and whole cell patch-clamp technique and compared with results from contractile experiments. Motilin and GM611 (0.01-100 nM) dose dependently produced slowly sustained depolarizations (half-maximal effective dose = 0.15 and 3.9 nM for motilin and GM611, respectively) but exhibited biphasic effects on spike activities superimposed on slow waves. With small depolarizations, the number of spike discharges increased, whereas larger depolarizations markedly reduced spike amplitude. Motilin-induced (or GM611-induced) depolarization appeared to be associated with the activation of monovalent cation-selective channels, and the reduction in the spike amplitude appeared mainly to be associated with inhibition of voltage-dependent Ca2+ channels. Furthermore, data from patch-clamp experiments suggested that Ca2+ release occurred from heparin-sensitive internal stores upon stimulation of motilin receptors by these agonists. Possible implications of these electrophysiological effects in motilin- or GM611-induced tonic and phasic contractions have been discussed.
Effects of potassium on magnesium transport across rumen epithelium
Authors: Leonhard-Marek S. , Martens H.
Published: December 2017

Increasing ruminal K concentration impairs active Mg transport across the forestomach epithelium of ruminants. We used Ussing chamber and microelectrode techniques to test the hypothesis that high mucosal K decreases the driving force for Mg2+ uptake by depolarizing the apical membrane. Serosal Ba enhanced net 42K secretion. Under open-circuit conditions, rumen epithelial cells showed an apical membrane potential (Va) of -67.3 +/- 1.5 mV. An increase in mucosal K concentration depolarized Va and decreased mucosal-to-serosal 28 Mg flux (Jm-->sMg). An increase in the transepithelial potential difference (Vt) depolarized Va, greatly decreased Jm-->sMg, and slightly increased Mg serosal-to-mucosal flux (Js-->mMg). Jm-->sMg exhibited an electrogenic and an electroneutral component. Mucosal verapamil depolarized Va and reduced Jm-->sMg, without affecting Js-->mMg. The study shows that rumen epithelial cells exhibit apical and basolateral K conductances and that transcellular Mg absorption has a distinct electrogenic component. This supports the assumption that a change in Va represents the link between increased ruminal K concentration and decreased Mg absorption. The results are discussed with regard to the development of hypomagnesemia in ruminants.
Protective effects of prostaglandin E1 on acute lung injury of caerulein-induced acute pancreatitis in rats
Authors: Yamanaka K. , Saluja A. K. , Brown G. E. , Yamaguchi Y. , Hofbauer B. , Steer M. L.
Published: December 2017

Infusion of a supramaximally stimulating dose of the pancreatic secretagogue caerulein (10 micrograms.kg-1.h-1) for 4 h induces interstitial edematous acute pancreatitis in rats. This model of acute pancreatitis is associated with evidence of acute lung injury, including sequestered neutrophils within the pulmonary microvasculature, increased microvascular permeability, and interstitial pulmonary edema. Infusion of prostaglandin E1 (PGE1; 50 ng.kg-1.min-1) along with caerulein does not alter the severity of secretagogue-induced pancreatitis, but it does reduce the severity of pancreatitis-associated acute lung injury. The rise in lung weight, lung water content, and pulmonary microvascular permeability and the sequestration of neutrophils within the pulmonary microvasculature that accompany secretagogue-induced pancreatitis are all reduced by infusion of PGE1. Infusion of PGE1 does not interfere with polymorphonuclear neutrophil sequestration in the pancreas or reduce the enhanced expression of CD11b/c receptors on circulating neutrophils. Our observations indicate that PGE1 reduces the severity of pancreatitis-associated acute lung injury by preventing neutrophil sequestration within the lung. We speculate that PGE1 interferes with neutrophil sequestration by dilating pulmonary vasculature, increasing pulmonary flow rate, and reducing neutrophil-endothelial cell interaction and attachment.
Prolactin increases ATP-dependent taurocholate transport in canalicular plasma membrane from rat liver
Authors: Liu Y. , Suchy F. J. , Silverman J. A. , Vore M.
Published: December 2017

The taurocholate (TC) maximal secretory rate (SRm) in the isolated perfused liver is increased in postpartum rats and ovariectomized rats treated with ovine prolactin (oPRL). The present studies were designed to characterize the mechanism(s) by which oPRL increases TC transport in the liver. oPRL (300 micrograms/day i.v. for 7 days) increased the SRm 1.6-fold from 185 to 364 nmol.min-1.mg protein-1 in the perfused rat liver and the maximal rate of transport for ATP-dependent transport 1.7-fold from 66 to 109 nmol.min-1.mg protein-1 in canalicular liver plasma membrane (cLPM) vesicles without changing the Michaelis constant (5-6 microM). The oPRL-mediated increases in biliary excretion in the perfused liver and ATP-dependent TC transport in cLPM vesicles were significantly inhibited by cycloheximide treatment (2 mg/kg). oPRL (300 micrograms/day iv for 7 days) increased expression of Ca(2+)-Mg(2+)-ecto-adenosinetriphosphatase mRNA sixfold and increased protein expression two- to threefold, but had no effect on the expression of P-glycoprotein (mdr1b and mdr2) mRNA. Thus the increase in ATP-dependent transport in cLPM vesicles due to oPRL treatment accounts for the increased TC SRm in the perfused liver. The oPRL-mediated increased TC transport may be associated with increased expression of proteins related to bile acid transport.
Net H+ and K+ fluxes across the apical surface of rat distal colon
Authors: Feldman G. M. , Ickes J. W.
Published: December 2017

The distal colon absorbs K+ (JK) and secretes H+ (JH) by what is thought to be an H(+)-K(+)-adenosinetriphosphatase (H(+)-K(+)-ATPase). However, the colonic ATPase differs structurally and functionally from the gastric H(+)-K(+)-ATPase. To evaluate the link between JH and JK, JH and JK were simultaneously measured with ion-specific electrodes in segments of rat distal colon. JH and JK averaged 0.40 +/- 0.03 and 0.30 +/- 0.03 mu eq.h-1.cm-2 (n = 191), but JH and JK did not correlate (r = 0.005, not significant). The gastric H(+)-K+ pump inhibitors SCH-28080 (100 microM) and omeprazole (100 microM), as well as a vacuolar H(+)-ATPase inhibitor, bafilomycin A1 (10 microM), did not affect JH or JK. However, the Na(+)-K(+)-ATPase inhibitors ouabain (1 mM) and N-ethylmaleimide (10 microM) inhibited JK but not JH. Although 1 mM orthovanadate inhibited both JH and JK, at lower concentrations orthovanadate only affected JK. Furthermore, removing K+ from the medium did not affect JH. Secondary hyperaldosteronism increased both JH and JK; however, ouabain (1 mM) reduced JK but not JH. Cl(-)-free medium inhibited voltage-insensitive JH and voltage-sensitive JK. Medium pH affected JH, but that effect was contrary to the effect that pH had on Rb+ flux. These data failed to identify a relationship between JH and JK and appear to suggest that JH and JK occur by separate pathways.
Effect of pharyngeal water stimulation on esophageal peristalsis and bolus transport
Authors: Bardan E. , Xie P. , Ren J. , Dua K. , Shaker R.
Published: December 2017

Sensory stimuli originating from the pharynx inhibit esophageal peristalsis induced by a dry swallow. Our aims were to determine the effect of these stimuli on esophageal bolus transport and esophageal peristalsis induced by swallowing different volumes of liquid and semisolid boluses. We studied nine healthy volunteers age 35 +/- 4 yr in the supine position by intraluminal esophageal manometry as well as concurrent videofluoroscopy and manometry. In all subjects progression of peristalsis induced by swallowing of different volumes of water and mashed potato boluses was inhibited at all sites by pharyngeal water injection. Threshold volume for inhibition of the peristalsis induced by swallows of 5 and 10 ml of water was similar but significantly higher compared with dry swallows (P < 0.05). Pharyngeal water injection invariably halted transit of the barium boluses through the esophagus. Sensory impulses originating from the pharynx 1) inhibit esophageal bolus transit and 2) are capable of overcoming the facilitating effect of a liquid bolus on the swallowing apparatus. This phenomenon may explain the mechanism of some of the failed esophageal peristalsis observed in clinical practice.
Central somatostatin prevents vagal efferent nerve excitation produced by TRH but not by 2-deoxy-D-glucose
Authors: Masuda M. , Kanai S. , Miyasaka K.
Published: December 2017

Thyrotropin-releasing hormone (TRH) administered intracerebroventricularly and intravenous injection of 2-deoxy-D-glucose (2-DG) stimulate pancreatic exocrine secretion via vagal efferent nerve excitation. We examined whether centrally administered somatostatin would inhibit pancreatic exocrine secretion that was stimulated by vagal efferent nerve excitation in conscious rats. The animals were prepared with cannulas draining bile and pancreatic juice separately and with a duodenal cannula, a cerebroventricular cannula, and a right jugular vein cannula. Intracerebroventricular injection of somatostatin (0.4 or 4 nmol) significantly inhibited pancreatic secretion induced by TRH (50 or 500 pmol) in a dose-dependent manner. Intravenous injection of somatostatin had no effect on pancreatic secretion stimulated by TRH. On the other hand, somatostatin injected centrally did not affect pancreatic secretion induced by 2-DG (75 mg/kg) or basal secretion. These results suggest that TRH and 2-DG stimulate vagal efferent nerves via distinct mechanisms and that central somatostatin selectively inhibits excitation of the vagus induced by peptidergic (TRH) stimulation.
Colonic mechanosensory afferent input to neurons in the mouse superior mesenteric ganglion
Authors: Miller S. M. , Szurszewski J. H.
Published: December 2017

Electrical activity and synaptic responses were recorded intracellularly in 415 neurons of the mouse superior mesenteric ganglion (SMG) attached to a segment of distal colon in vitro. Eighty-seven percent of neurons tested received ongoing nicotinic cholinergic fast excitatory postsynaptic potentials (fEPSPs). Colonic distension caused an initial transient followed by a sustained, slowly adapting increase in fEPSP activity. Application of hexamethonium only to the colon reduced, but did not completely abolish, distension-evoked responses, suggesting direct projection of some distension-sensitive fibers. Ongoing fEPSPs were abolished when nerve trunks connecting the SMG to the colon were transected or blocked with tetrodotoxin applied to the colon. Intracellular labeling with horseradish peroxidase or lucifer yellow revealed that about 90% of neurons receiving colonic synaptic input had a caudally projecting axon; about 60% that did not receive colonic input had a rostrally projecting axon. The latter neurons were found only in the cephalad ganglion region. These results show that mouse SMG neurons receive colonic mechanosensory afferent synaptic input and thus may participate in sympathetic intestinal reflexes.
Constitutive expression of inducible nitric oxide synthase in the mouse ileal mucosa
Authors: Hoffman R. A. , Zhang G. , Nussler N. C. , Gleixner S. L. , Ford H. R. , Simmons R. L. , Watkins S. C.
Published: December 2017

It has been demonstrated previously that the inducible isoform of nitric oxide synthase (iNOS) is present throughout the intestinal tract in various inflammatory disease processes. Here we demonstrate that iNOS mRNA is present in the ileum but not in the jejunum or colon of normal mice. By Western blot analysis, iNOS protein is also detected in normal ileum, but not in the normal jejunum. However, by 3 h postinjection of 0.5 mg/kg lipopolysaccharide (LPS), iNOS mRNA is also detectable in the jejunum and colon. The enzyme message and protein, localized immunohistochemically by in situ hybridization and iNOS expression, is normally restricted to the villus epithelial cells. The iNOS mRNA was also present in the ilea of mice with defined intestinal flora (anaerobes only), germ-free mice, nude mice, and to a lesser extent in mice with severe combined immunodeficiency. These results suggest that the constitutive presence of iNOS in ileal epithelium indicates a role for this enzyme in maintaining intestinal homeostasis.
Differing mechanisms of stimulation of Na+ absorption in rabbit proximal colon
Authors: Sellin J. H. , Desoignie R.
Published: December 2017

Both alpha2-adrenergic agonists and decreased Na+ in the bathing fluids stimulate electroneutral Na+ absorption in rabbit proximal colon, but it is unclear whether they have similar modes of action. We sought to define regulatory events involved with stimulation of Na+ absorption by these two agonists. Transport parameters were assessed by ion flux studies under short-circuit and pH stat conditions, recordings of intracellular electrical potential difference (psi(mc)) with microelectrode impalements, and measurement of intracellular pH (pH(i)). Epinephrine elicited a yohimbine-inhibitable alkalinization of pH(i) but did not alter psi(mc) In contrast, lowered serosal Na+ concentration ([Na+]) did not significantly increase pH(i) but did depolarize psi(mc). Removal of serosal HCO(3)- stimulated Na+ absorption and reversed residual ion flux from secretion to absorption. pH stat studies demonstrated epinephrine-stimulated, amiloride-inhibitable serosal alkalinization. Serosal 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid inhibited Na+ absorption. Epinephrine and lowered [Na+] have different effects on intracellular parameters associated with electroneutral Na+ absorption. Epinephrine stimulates an apical Na+/H+ exchanger. Lowered [Na+] elicits responses consistent with a coupled Na+-HCO(3x)- exit step. Coordinated function of apical Na+/H+ exchangers and a basolateral Na+-HCO(3)(x)- symport permit Cl(-)-independent electroneutral Na+ absorption while maintaining pH(i) homeostasis. Given the low [Cl-] environment of the colonic lumen, this transport pathway may be important for electroneutral Na+ absorption.
Dietary fructose enhances intestinal fructose transport and GLUT5 expression in weaning rats
Authors: Shu R. , David E. S. , Ferraris R. P.
Published: December 2017

Rates of fructose uptake by the small intestine of neonatal rats are typically very low from parturition through weaning but undergo a dramatic increase immediately after weaning is completed. In this study, we used intestinal fructose transport as a model to determine whether nutrient transport, normally enhanced only after completion of weaning, can be enhanced earlier during development. We found that ontogenetic changes in levels of GLUT5 mRNA correlate well with already known ontogenetic changes in rates of intestinal fructose transport: low levels and rates during suckling and weaning, and high levels and rates after weaning. In contrast, levels of GLUT2 and SGLT1 mRNA were relatively more elevated throughout the suckling and weaning periods. We then found that increased expression of GLUT5 mRNA caused by dietary fructose or sucrose paralleled diet-dependent increases in brush-border fructose uptake. Rates of brush-border glucose uptake and levels of SGLT1 and GLUT2 mRNA were not enhanced by dietary fructose, glucose, or sucrose. Finally, we found that rates of fructose uptake, levels of GLUT5 mRNA, and specific sucrase activity each increased with increasing concentrations of dietary fructose given precociously to midweaning rats. In contrast, brush-border glucose uptake was independent of dietary fructose concentration. Thus precocious introduction of dietary fructose causes enhanced expression of fructose transporters earlier during development. This effect is specific: only luminal fructose is effective, and only brush-border fructose transport can be modulated. These results unveil the potential for regulating nutrient transport early in development.
Systemic infusion of IGF-I or LR(3)IGF-I stimulates visceral organ growth and proliferation of gut tissues in suckling rats
Authors: Steeb C. B. , Shoubridge C. A. , Tivey D. R. , Read L. C.
Published: December 2017

This study describes developmental changes in gastrointestinal response to insulin-like growth factor I (IGF-I) peptide administration. Neonatal rats were infused with IGF-I or long [Arg3]IGF-I (LR(3)IGF-I) for 6.5 days starting on day 6 or 12 postpartum. Peptides were delivered by mini osmotic pumps at 0, 2, 5, or 12.5 microg x g(-1) x day(-1). IGF-I infusion increased plasma IGF-I levels in both age groups but stimulated body weight gain only in the older rats. Infusion of LR(3)IGF-I did not change plasma IGF-I levels. Both peptides enhanced expression of IGF-binding proteins (IGFBP) 1 and 2 and induced IGFBP-3 in the older rats. For both age groups, weights of the kidney and spleen increased by up to 85 and 76%, respectively. IGF-I treatment also stimulated gut weight and length by up to 60 and 32%, respectively, but dose dependency was observed only in the older rats. LR(3)IGF-I was more potent for all growth parameters in both age groups. Histological observations included thickening of the mucosa and muscularis externa after infusion of IGF-I peptides. Thymidine labeling in the younger rats indicated that proliferative activity increased proportionately with crypt cell growth. These results show that IGF-I peptides selectively stimulate growth of gastrointestinal tissues in suckling rats and that the proximal gut was the most peptide-responsive region.
Increased C/EBP in fetal rat small intestine precedes initiation of differentiation marker mRNA synthesis
Authors: Montgomery R. K. , Rings E. H. , Thompson J. F. , Schuijt C. C. , Aras K. M. , Wielenga V. J. , Kothe M. J. , Buller H. A. , Grand R. J.
Published: December 2017

Morphogenesis, initiation of differentiation marker gene expression, and their correlation with CCAT/enhancer binding protein (C/EBP) expression were analyzed in the developing fetal rat small intestine. Expressions of mRNAs for lactase-phlorizin hydrolase (LPH), intestinal alkaline phosphatase (IALP), carbamoyl-phosphate synthetase (CPS), and three isoforms of C/EBP were simultaneously determined by Northern blot analysis from 15 to 19 days of gestation. At 17 days of gestation, prior to villus formation as demonstrated by light and electron microscopy, only CPS and C/EBPalpha, -beta, and -delta expression could clearly be detected. Both LPH and IALP mRNA were definitely detectable in proximal and middle intestine on day 18, as soon as the stratified epithelium of the early intestine had been transformed into a single layer of columnar epithelium lining villi. This distribution was confirmed by in situ hybridization for LPH mRNA. During the period of transformation when the columnar epithelium and villi were forming, no LPH or IALP mRNA was detectable in the immature distal one-third of the fetal intestine. Preceding villus morphogenesis, immunostaining demonstrated nuclear localization of C/EBPalpha protein in intestinal epithelial cells, with continued expression in all enterocytes through 19 days of gestation. Enhanced expression of C/EBPalpha mRNA and protein began 24 h prior to the initiation of the differentiation markers, suggesting that it may play a role in regulation of fetal intestinal differentiation.
Systemic and hepatic hemodynamic changes in acute liver injury
Authors: Makin A. J. , Hughes R. D. , Williams R.
Published: December 2017

Systemic and hepatic circulatory changes were studied in rats over the course of acute liver injury. Hepatic injury was induced by intraperitoneal injection of D-galactosamine (1.1 g/kg), and systemic and hepatic hemodynamics were measured over a 72-h period using a radioactive microsphere technique with direct measurement of arterial, portal venous, and hepatic venous blood oxygen content. Cardiac output increased to a maximum at 48 h, producing a marked increase (450%) in hepatic arterial blood flow so that it became the dominant supply of oxygen at the time of maximal hepatic injury. A subsequent increase in portal venous flow resulted in an overall increase in total hepatic blood flow of 500%. At this point the oxygen delivery by the hepatic arterial and portal venous systems was equal. These circulatory changes returned to control values by 72 h with recovery of liver function. These results demonstrate the development of a hyperdynamic circulation and a marked change in the normal relationship between portal venous and hepatic arterial blood flows that occur during hepatic injury.
Immunohistochemical localization of cysteine-rich intestinal protein in rat small intestine
Authors: Fernandes P. R. , Samuelson D. A. , Clark W. R. , Cousins R. J.
Published: December 2017

Cysteine-rich intestinal protein (CRIP) is a LIM (cysteine-rich motif of leu-11, isl-1, and mec-3 genes) domain protein with a double zinc finger motif. The protein is abundantly expressed in the intestine, peritoneal macrophages, and peripheral blood mononuclear cells. The function of CRIP is not known. The purpose of this study was to determine the cellular distribution of CRIP in rat intestine, as an initial step toward eventual determination of a function. Immunohistochemical and immunogold labeling electron microscopy using a purified polyclonal rabbit antibody to a synthetic peptide representing a zinc finger domain of rat CRIP were carried out on sections of rat duodenum. Western blotting was used to detect signal specificity of the antibodies. These immunohistochemical and electron microscopy studies showed particularly high abundance of CRIP in the cytoplasmic granules of Paneth cells of the intestine. Some evidence of CRIP expression was also found in cells of the villus tip, but abundance was less than that found in the Paneth cells. The localization of CRIP in Paneth cells and its presence in mononuclear cells suggests that CRIP may be involved in host defense mechanisms and/or tissue differentiation/remodeling processes common to these cell types.
CFTR mediates cAMP- and Ca2+-activated duodenal epithelial HCO3- secretion
Authors: Hogan D. L. , Crombie D. L. , Isenberg J. I. , Svendsen P. , Schaffalitzky de Muckadell O. B. , Ainsworth M. A.
Published: December 2017

The role of the cystic fibrosis transmembrane conductance regulator (CFTR) in duodenal alkaline secretion has not been directly examined. The aims of this series of experiments were to determine if CFTR mediates basal and stimulated duodenal epithelial HCO3- secretion. Utilizing the cystic fibrosis murine model (cftr(m1UNC)), we compared normal [CFTR(+/+)] littermates (34-46 days old) with CFTR(-/-) animals (34-39 days old). Anesthesia was induced and maintained with intraperitoneal Hypnorm-midazolam. The proximal duodenum (4-7 mm) was cannulated and perfused with 154 mM NaCl. Either forskolin (10(-6)-10(-4) M) or carbachol (10(-6)-10(-3) M) was perfused intraluminally to activate adenosine 3',5'-cyclic monophosphate (cAMP)- and Ca2+-mediated HCO3- secretion, respectively. Effluent volumes were weighed and HCO3- quantitated by back titration. Basal HCO3- secretion was diminished significantly (P < 0.01) in CFTR(-/-)vs. normal CFTR(+/+) mice (2.8 +/- 0.5 vs. 5.3 +/- 0.4 micromol x cm(-1) x h(-1)). Moreover, in CFTR(-/-) mice, both forskolin- and carbachol-stimulated peak HCO3- secretions were fourfold less compared with those in CFTR(+/+) littermates (3.7 +/- 0.2 vs. 15.6 +/- 2.1 and 4.7 +/- 0.3 vs. 14.2 +/- 2.5 micromol x cm(-1) x h(-1), respectively; P < 0.01). In conclusion, CFTR plays a significant role in mediating basal, cAMP-, and Ca2+-activated duodenal epithelial HCO3- secretion.
Regulation and translocation of ATP-dependent apical membrane proteins in rat liver
Authors: Gatmaitan Z. C. , Nies A. T. , Arias I. M.
Published: December 2017

The bile canalicular membrane contains four specific ATP-dependent transport processes that are involved in secretion of bile acids, non-bile acid organic anions (mrp1), phospholipids (mdr2), and organic cations (mdr3). The aim of this study was to determine how the canalicular presence of these transport proteins is regulated. Canalicular membrane vesicles (CMV) were prepared from livers of rats treated with taurocholate (TC) and/or dibutyryl-adenosine 3',5'-cycle monophosphate (DBcAMP) with and without pretreatment with colchicine. Transport studies were performed with radiolabeled substrates. Changes in the relative amounts of transport proteins were determined by Western blots. Compared with controls, the specific activity of each of the transport processes was enhanced 1.5- and 3-fold with TC and DBcAMP treatments, respectively. Western blots revealed the same increases with mdr2 and mdr3. Pretreatment of rats with colchicine prevented these responses fully with TC treatment, whereas only partial prevention was obtained with DBcAMP treatment. Besides the ATP-dependent transporters, the relative specific activities of the canalicular membrane ectoenzyme markers, leucine aminopeptidase and gamma-glutamyltranspeptidase, were also affected the same way. These results suggest that TC and DBcAMP increase the specific activity of the canalicular ATP-dependent transport proteins and some canalicular membrane ectoenzymes by stimulating an increase in the relative amounts of these proteins in the membrane.
The role of antioxidant enzymes in the control of opossum sphincter of Oddi motility
Authors: Cullen J. J. , Herrmann B. M. , Thomas R. M. , Fang S. , Murray J. A. , Ledlow A. , Christensen J. , Conklin J. L.
Published: December 2017

Superoxide rapidly oxidizes nitric oxide (NO) to form peroxynitrite, thus terminating the biological activity of NO. The aims of our study were to determine if superoxide alters the motor function of the sphincter of Oddi and to localize the antioxidant enzymes in the sphincter of Oddi. Immunostaining was performed and enzyme activities were measured in the sphincter of Oddi. In physiological experiments, force-displacement transducers recorded tension in the spontaneously contracting sphincter of Oddi and after electrical field stimulation (EFS) of precontracted sphincter of Oddi. Superoxide was generated by the addition of xanthine with xanthine oxidase, superoxide radicals were scavenged by the addition of superoxide dismutase (SOD), and catalase or SOD was inhibited by diethyldithiocarbamic acid. Immunostaining demonstrated SOD and catalase immunoreactivity in ganglia situated at the serosal surface of the circular muscle. Total SOD activity was 202 +/- 12 U/mg. Generation of superoxide or inhibition of SOD increased the contractile frequency and decreased relaxation after EFS. We conclude that superoxide alters sphincter of Oddi motor function, and the presence of superoxide scavenging enzymes in enteric plexuses suggests that they may regulate sphincter of Oddi neuromuscular function by clearing endogenous superoxide.
Glucocorticoids inhibit mitochondrial matrix acyl-CoA dehydrogenases and fatty acid beta-oxidation
Authors: Letteron P. , Brahimi-Bourouina N. , Robin M. A. , Moreau A. , Feldmann G. , Pessayre D.
Published: December 2017

Glucocorticoid administration may produce fatty liver in humans. We investigated the effects of dexamethasone on hepatic mitochondria and lipid metabolism in mice. Dexamethasone 21-phosphate (20 microM) did not inhibit the mitochondrial inner membrane-bound very-long-chain acyl-CoA dehydrogenase but inhibited the matrixlocated long-, medium-, and short-chain dehydrogenases. Dexamethasone 21-phosphate (20 microM) inhibited the first beta-oxidation cycle of [1-(14C)]butyric acid and [1-(14C)]octanoic acid but not that of [1-(14C)]palmitic acid. Administration of dexamethasone 21-phosphate (100 mg/kg) decreased the in vivo oxidation of [1-(14C)]butyric acid and [1-(14C)]octanoic acid into [14C]CO2 but not that of [1-(14C)]palmitic acid and decreased the hepatic secretion of triglycerides. After 5 days of treatment (100 mg/kg daily), hepatic triglycerides were increased and both microvesicular steatosis and ultrastructural mitochondrial lesions were present. In conclusion, glucocorticoids inhibit medium- and short-chain acyl-CoA dehydrogenation and hepatic lipid secretion in mice. These effects may account for their steatogenic effects in humans.
Female rats exhibit greater susceptibility to early alcohol-induced liver injury than males
Authors: Iimuro Y. , Frankenberg M. V. , Arteel G. E. , Bradford B. U. , Wall C. A. , Thurman R. G.
Published: December 2017

It is known that women develop hepatic injury more rapidly and with exposure to less ethanol than men; however, mechanisms remain unclear. The purpose of this study was to determine if an enteral alcohol delivery model could be used to study susceptibility of females to alcohol-induced liver injury. Male and female Wistar rats (age- or weight-matched) were given ethanol (11-12 g.kg-1.day-1) continuously for up to 4 wk via intragastric feeding, and control rats received a high-fat diet without ethanol. There were no significant differences in body weight among the groups studied. Furthermore, mean ethanol concentrations, their cyclic pattern in urine, and rates of ethanol elimination were also not different between the genders under these conditions. Ethanol treatment elevated serum aspartate aminotransferase levels in male rats to 126 +/- 10 IU/l after 4 wk. In females, however, values increased more rapidly and reached significantly higher values at 4 wk (168 +/- 18 IU/l). Steatosis, inflammation, and necrosis assessed histologically also developed more rapidly and were more severe in females than males. Steatosis due to ethanol exposure, which was localized in centrilobular areas in males, was panlobular in the female. Moreover, endotoxin in plasma, intercellular adhesion molecule 1 expression in hepatic sinusoidal-lining cells, and the number of infiltrating inflammatory cells in the liver were 2-2.5-fold greater in females than males. These changes possibly account for increased hepatic injury due to ethanol in the female.
Neutrophil margination and extravasation in sinusoids and venules of liver during endotoxin-induced injury
Authors: Chosay J. G. , Essani N. A. , Dunn C. J. , Jaeschke H.
Published: December 2017

Neutrophils contribute to liver damage during endotoxin shock. The objective of this investigation was to document where neutrophils localize in the hepatic vasculature and whether they migrate out of sinusoids or postsinusoidal venules. A well-characterized model of galactosamine and endotoxin shock and immunostaining for neutrophil-associated migration inhibition factor-related protein complex 8/14 S100 calcium-binding proteins were used. Treatment of C3Heb/FeJ mice with 100 micrograms/kg Salmonella abortus equi endotoxin alone or in combination with 700 mg/kg galactosamine induced a time-dependent increase of neutrophil margination in sinusoids and postsinusoidal venules at 4 h. The number of venular neutrophils decreased in both groups at later time points without evidence for transmigration. Extravasation of neutrophils was only observed from sinusoids in galactosamine plus endotoxin-treated animals between 4 and 7 h, which correlated with parenchymal cell injury. After endotoxin alone, large numbers of neutrophils remained sequestered in sinusoids without injury. These data suggest that neutrophils cause hepatocellular injury during endotoxemia after extravasation and are less likely to cause damage when sequestered in the vasculature. In the liver, neutrophils migrate out of sinusoids and not out of postsinusoidal venules.
Endogenous carbon monoxide suppression stimulates bile acid-dependent biliary transport in perfused rat liver
Authors: Sano T. , Shiomi M. , Wakabayashi Y. , Shinoda Y. , Goda N. , Yamaguchi T. , Nimura Y. , Ishimura Y. , Suematsu M.
Published: December 2017

This study aimed to investigate whether carbon monoxide (CO), a product of heme oxygenase that degrades protoheme IX, serves as an endogenous modulator for biliary transport. To that end, effects of zinc protoporphyrin IX (ZnPP), a heme oxygenase inhibitor, on the biliary transport were tested in perfused rat liver. Perfusion of 1 microM ZnPP abolished detectable levels of CO in the venous perfusate and increased bile acid-dependent bile output accompanying an increased secretion of bile salts. The ZnPP-induced choleresis coincided with a reduction of tissue guanosine 3',5'-cyclic monophosphate (cGMP) levels and a decrease in vascular conductance. On administration of 2.5 microM CO, ZnPP-elicited choleresis, decreases in vascular conductance, and cGMP levels were all attenuated. Treatment with 1 microM 8-bromoguanosine 3',5'-cyclic monophosphate (8-BrcGMP) partly attenuated the ZnPP-induced choleresis in concert with repression of vascular conductance. Furthermore, treatment of the liver with methylene blue, a guanylate cyclase inhibitor, evoked a choleresis similar to that induced by ZnPP. Thus endogenous CO suppression stimulates the biliary transport in part through a cGMP-dependent mechanism.