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1
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A downregulation of nNOS is associated to dysmotility evoked by lipopolysaccharide in rabbit duodenum

100%
Grasa L., Arruebo M. P., Plaza M. A., Murillo M. D.
Journal of Physiology and Pharmacology
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2008
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tom 59
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nr 3
511-524
Alterations in gastrointestinal motility have been reported in response to endotoxin. The effects of lipopolysaccharide (LPS) on motility have been attributed to several substances, including prostaglandins and nitric oxide. The aim of this study was to investigate the expression and the contribution of NOS and COX enzymes to the local effect of LPS on ACh-evoked contractions in rabbit duodenum. The ACh evoked contractions were inhibited by LPS in longitudinal and circular muscles of duodenum. L-NNA, aminoguanidine, ODQ, indomethacin, and NS-398 but not NPLA antagonized the inhibitory effect of LPS. Western blot analysis showed protein bands of 155, 130, 70 and 72 kDa for nNOS, iNOS, COX-1 and COX-2 respectively in rabbit duodenum. All of these isoforms were expressed constitutively and only the nNOS was reduced in the presence of LPS. Expression of nNOS, iNOS, COX-1 and COX-2 was detected by inmunohistochemistry in the smooth muscle layers and in the neurons of the myenteric ganglia of rabbit duodenum. In conclusion, LPS locally administered reduces the contractility of rabbit duodenum and a downregulation of nNOS is associated to this effect. The iNOS, COX-1 and COX-2 were expressed constitutively but their expression was not modified by LPS.
2
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The role of tyrosine kinase in prostaglandin E2 and vanadate-evoked contractions in rabbit duodenum in vitro

100%
Grasa L., Arruebo M. P., Plaza M. A., Murillo M. D.
Journal of Physiology and Pharmacology
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2006
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tom 57
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nr 2
Prostaglandin E2 (PGE2) can interact with at least four cell surface receptors (EP1-EP4) in smooth muscle, which evokes a variety of intracellular responses depending on the G protein to which the cell surface receptors are coupled. The activation of G protein-coupled receptors and receptor tyrosine kinases can lead to the phosphorylation of tyrosine residues of various cellular proteins. The aim of this study was to examine the role of tyrosine phosphorylation in PGE2, vanadate and carbachol-evoked contractions. PGE2, vanadate, and carbachol induced contractile motor responses in the longitudinal smooth muscle of rabbit duodenum. PGE2-evoked contractions decreased in the presence of genistein or tyrphostin B44. PGE2-evoked contractions increased in the presence of vanadate. Vanadate-evoked contractions decreased in the presence of genistein. In contrast, tyrphostin 47 increased the vanadate-evoked contractions. Vanadate-evoked contractions were reduced in the presence of Ca2+-free solutions, verapamil, or indomethacin. U-73122 decreased PGE2-evoked contractions. Carbachol-evoked contractions decreased in the presence of genistein, tyrphostin B44 or tyrphostin 47. Our results suggest that PGE2, vanadate or carbachol-evoked contractions are mediated by protein tyrosine phosphorylation. Protein tyrosine phosphorylation might cause an increase in calcium influx through voltage-dependent channels and the release of prostaglandins in the longitudinal smooth muscle of the rabbit duodenum.
3
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The role of Ca2plus in the contractility of rabbit small intestine in vitro

88%
Grasa L., Rebollar E., Arruebo M. P., Plaza M. A., Murillo M. D.
Journal of Physiology and Pharmacology
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2004
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tom 55
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nr 3
This study evaluated the role of Ca2+ in spontaneous and ACh- and KCl-induced contractions in longitudinal and circular smooth muscle from rabbit small intestine in vitro. In the first experiment, the amplitude, frequency and tone of spontaneous contractions in longitudinal and circular smooth muscle of small intestine were determined and, in the second experiment, the ACh- and KCl-induced responses of longitudinal and circular smooth muscle were measured. Atropine and guanethidine reduced the amplitude and tone of contractions in longitudinal and circular muscle, but reduced the frequency of contractions in circular muscle, only. TTX attenuated the amplitude of contractions and decreased the tone of contractions in longitudinal muscle, but increased the tone in circular muscle. Ca2+-free solutions, verapamil, nifedipine and caffeine diminished the three parameters of spontaneous contractions. Thapsigargin and cyclopiazonic acid increased the amplitude and tone of contractions in ileum longitudinal muscle, only, and cyclopiazonic acid increased the amplitude of contractions in circular muscle. Ca2+-free solutions, verapamil, nifedipine, thapsigargin, cyclopiazonic acid, and caffeine diminished ACh- and KCl-induced contractions. Those results suggest that extracellular Ca2+ plays a role in spontaneous contractions, and extracellular and intracellular Ca2+ participate in the ACh- and KCl-induced contractions of rabbit small intestine.
4
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The role of NO in the contractility of rabbit small intestine in vitro: effect of K+ channels

88%
Grasa L., Rebollar E., Arruebo M. P., Plaza M. A., Murillo M. D.
Journal of Physiology and Pharmacology
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2005
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tom 56
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nr 3
Nitric oxide (NO) is an inhibitory neurotransmitter of intestinal smooth muscle cells. The aim of this study was to determine the role of NO in the contractility of rabbit small intestine smooth muscle in vitro. The amplitude, frequency and tone of spontaneous contractions in longitudinal and circular smooth muscle of duodenum, jejunum and ileum were determined and the sodium nitroprusside (SNP), acetylcholine (ACh) and KCl responses were quantified. L-NAME, L-NNA, L-arginine and D-arginine did not affect the amplitude, frequency and tone of spontaneous contractions. ODQ (10-6 M) increased the tone of spontaneous contractions of the types of tissues examined, and the amplitude in ileum, without modifying the frequency. SNP (10-4 M) evoked relaxations that were not influenced by atropine (10-6 M) plus guanethidine (10-6 M), apamin (10-8 M) or glybenclamide (10-6 M), but were increased by TTX (10-6 M) and verapamil (10-7 M). SNP-induced relaxations were reduced by charybdotoxin (10-8 M) and ODQ (10-6 M). ODQ (10-5 M) reduced ACh-induced contractions, but it did not influence KCl-evoked contractions. Those results suggest that NO modulates the spontaneous contractions of small intestine in rabbits. This effect is mediated by cGMP and Ca2+-dependent K+ channels of large conductance.
5
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Role of potassium channels in rabbit intestinal motility disorders induced by 2,2'-azobis [2-amidinopropane] dihydrochloride [AAPH]

76%
Hernandez L., Grasa L., Fagundes D. S., Gonzalo S., Arruebo M. P., Plaza M. A., Murillo M. D.
Journal of Physiology and Pharmacology
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2010
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tom 61
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nr 3
279-286
Oxidative stress appears to play a role in the pathogenesis of several inflammatory gastrointestinal diseases. Changes in intestinal motility have been reported in different models of intestinal inflammation. The initiating factor of altered motility could be an alteration of gut redox status. The aim of this study was to investigate the effect of oxidative stress evoked by 2, 2´-azobis (2-amidinopropane) dihydrochloride (AAPH) on the intestinal motility of rabbit duodenum and the possible contribution of different K+ channels in mediating this response. Whole thickness segments of rabbit duodenum were suspended in the direction of the longitudinal or circular smooth muscle fibres in an organ bath to study the effects of AAPH alone, or in the presence of different K+ channel blockers on the amplitude, frequency and tone of spontaneous contractions. In circular muscle, AAPH 20 mM induced a reduction of the amplitude, the frequency and tone of the spontaneous contractions. In longitudinal muscle, AAPH 10 mM induced a reduction of the amplitude and tone of the spontaneous contractions. The reduction of the amplitude and tone induced by AAPH was reverted by BaCl2 (1 mM) and TEA (5 mM). Charybdotoxin (100 nM) and iberiotoxin (100 nM) only reverted the reduction of the tone induced by AAPH. In conclusion, our results show that the peroxyl radicals released by AAPH reduced the amplitude and the tone of the spontaneous contractions of the longitudinal smooth muscle from rabbit small intestine. Inward rectifier and intermediate and large-conductance Ca2+-activated K+ channels could be involved in these effects.
6
Content available remote

Mechanism of action of Trolox on duodenal contractility

76%
Fagundes D. S., Grasa L., Gonzalo S., Martinez de Salinas F., Arruebo M. P., Plaza M. A., Murillo M. D.
Journal of Physiology and Pharmacology
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2013
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tom 64
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nr 6
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