Search results for "Enterochromaffin cell"

2019

The P-STS human ileal neuroendocrine tumor cells, as a model for gut enterochromaffin cells, are strongly and synergistically activated by histamine plus acetylcholine (ACh), presumably via histamine 4 receptors, and weakly activated by histamine alone. Sensing these signals, enterochromaffin cells could participate in intestinal intolerance or allergic reactions to food constituents associated with elevated histamine levels. In this study we aimed to analyze the underlying molecular mechanisms. Inhibition by mepyramine and mibefradil indicated that histamine alone caused a rise in intracellular calcium concentration ([Ca2+]i) via histamine 1 receptors involving T-type voltage-gated calciu…

Effects of cigarette smoking or ingestion of nicotine on platelet 5-hydroxytryptamine (5-HT) levels in smokers and non-smokers.

1992

Platelets of healthy smokers and non-smokers were prepared and their content of 5-hydroxytryptamine was determined by HPLC with electrochemical detection. Platelet 5-HT levels in smokers (728 +/- 156 pmol per 10(8) platelets, mean +/- SEM, n = 9) were significantly higher than those in non-smokers (353 +/- 156 pmol per 10(8) platelets, n = 11). Smoking of a single cigarette caused a transient increase in platelet 5-HT levels by about 350% in non-smokers, but had no additional effect in smokers. Similarly, chewing of nicotine gum (4-8 mg nicotine) resulted in a transient increase in platelet 5-HT by about 100% in non-smokers, but not in smokers. In conclusion, smoking of cigarettes can cause…

Modulation by 5-HT3 and 5-HT4 receptors of the release of 5-hydroxytryptamine from the guinea-pig small intestine.

1993

The effects of agonists and antagonists of 5-hydroxytryptamine (5-HT) receptors on the release of endogenous 5-HT from enterochromaffin cells were studied in the vascularly perfused isolated guinea-pig small intestine. The experiments were done in the presence of tetrodotoxin in order to exclude a neuronally mediated influence on 5-HT release. The 5-HT3 receptor agonist 2-methyl-5-HT increased 5-HT release, and this effect was antagonized by 1 nmol/l tropisetron. Nanomolar concentrations of tropisetron, MDL 72,222 and granisetron decreased 5-HT release. Ondansetron (0.1 and 1 mumol/l) did not modify 5-HT release. 5-Methoxytryptamine, BIMU8 and cisapride concentration-dependently inhibited 5…

The human gene encoding cytokeratin 20 and its expression during fetal development and in gastrointestinal carcinomas

1993

The differentiation of the predominant cell types of the mucosal epithelium of the mammalian gastrointestinal tract is characterized by increasing amounts of an intermediate-sized filament (IF) protein designated cytokeratin (CK) 20 which is a major cellular protein of mature enterocytes and goblet cells. Here we report the isolation of the human gene encoding CK 20, its complete nucleotide sequence and the amino acid sequence deduced therefrom that identifies this polypeptide (mol. wt. 48553) as a member of the type I-CK subfamily. Remarkable, however, is the comparably great sequence divergence of CK 20 from all other known type I-CKs, with only 58% identical amino acids in the conserved …

Histamine inhibits 5-hydroxytryptamine release from the porcine small intestine: Involvement of H3 receptors

1992

Abstract Strips of the porcine small intestine were incubated in vitro, and the release of 5-hydroxytryptamine (5-HT) was determined by high-pressure liquid chromatography with electrochemical detection. Removal of the mucosa resulted in a large reduction (95%) of tissue 5-HT, suggesting that enterochromaffin cells are the main source of 5-HT. The release of 5-HT was reduced by 70% after omission of calcium. Tetrodotoxin and hexamethonium reduced the release of 5-HT by 30%–40% in a nonadditive manner, indicating a spontaneous neuronal (nicotinic) excitatory input to the enterochromaffin cells. Histamine inhibited the release of 5-HT by about 50%. This effect was not affected by mepyramine o…

NK1- and NK3-receptor mediated inhibition of 5-hydroxytryptamine release from the vascularly perfused small intestine of the guinea-pig

1997

The effects of tachykinins on the spontaneous release of 5-hydroxytryptamine (5-HT) from the enterochromaffin cells into the portal circulation was investigated in vitro using the vascularly perfused isolated guinea-pig small intestine. 5-HT was determined by HPLC with electrochemical detection. Test substances were applied intraarterially. Substance P (SP) caused a concentration-dependent decrease in 5-HT outflow with an EC50 of 50 pmol/l. Similarly, the selective NK1 receptor agonist SP methyl ester (1 nmol/l) significantly inhibited 5-HT outflow (to 51 +/- 3%). When tetrodotoxin (1 mumol/l) was added to the arterial perfusion medium, the inhibition by SP of 5-HT outflow was not affected.…

Spontaneous release of endogenous 5-hydroxytryptamine and 5-hydroxyindoleacetic acid from the isolated vascularly perfused ileum of the guinea-pig

1987

The spontaneous release of 5-hydroxytryptamine and its metabolite 5-hydroxyindoleacetic acid from the enterochromaffin cells of the small intestine into the portal circulation was investigated in vitro using the vascularly perfused ileum of the guinea-pig. The release of 5-hydroxytryptamine decreased by 70% in a calcium-free medium and by 35% in the presence of tetrodotoxin. Inhibition of monoamine oxidase activity by pargyline (100 microM) had no effect on the spontaneous release of 5-hydroxytryptamine although it caused a 75% reduction in the outflow of 5-hydroxyindoleacetic acid. Imipramine (1 microM), an inhibitor of neuronal uptake of 5-hydroxytryptamine, reduced the 5-hydroxyindoleace…

Nicotinic and muscarinic modulation of 5-hydroxytryptamine (5-HT) release from porcine and canine small intestine

1992

Strips of porcine and canine small intestine were incubated in vitro and the release of 5-hydroxytryptamine (5-HT) was determined by HPLC with electrochemical detection. The spontaneous outflow of 5-HT from the porcine and canine small intestine largely reflects calcium-dependent 5-HT secretion from enterochromaffin cells which are under a spontaneous neuronal, excitatory input as indicated by the inhibitory effect (30-40%) of tetrodotoxin. In both species, nicotine enhanced the release of 5-HT in a concentration-dependent manner by a maximum of about 50% at 100 microM. This effect was blocked by the nicotine receptor antagonist hexamethonium, but not by the subtype-selective nicotine recep…

Evidence that neuronally released vasoactive intestinal polypeptide inhibits the release of serotonin from enterochromaffin cells of the guinea pig s…

1991

Abstract. Isolated small intestinal segments of the guinea pig were arterially perfused and the release of serotonin (5-hydroxytryptamine) and 5-hydroxyindoleacetic acid into the portal venous effluent was determined by HPLC with electrochemical detection. Test substances were intra-arterially applied. The muscarine receptor agonist oxotremorine (1 μmol/l inhibited the release of 5-hydroxytryptamine by about 50%. In the presence of the neurotoxin tetrodotoxin, oxotremorine enhanced the release of 5-hydroxytryptamine by 145%, indicating that the inhibitory effect of oxotremorine was mediated by the release of a neurotransmitter. Exogenous vasoactive intestinal polypeptide ( 1-100 pmol/l inhi…

Temperature-dependent effects of increased intraluminal pressure on serotonin release from the vascularly perfused guinea pig ileum

1987

Isolated segments of the guinea pig ileum were vascularly perfused and the release of endogenous serotonin into the portal effluent was measured. Peristalsis was induced by raising the intraluminal hydrostatic pressure by 500 Pa for 5 min. Serotonin release increased during peristalsis induced by fluid of 37 degrees C, but decreased when the temperature of the intraluminal fluid was between 13 degrees C and 22 degrees C. In the presence of naloxone (0.3 mumol/l) raising the intraluminal pressure with fluid of 37 degrees C caused an inhibition of the serotonin release which was blocked by scopolamine (0.1 mumol/l). Naloxone did not affect the inhibition of serotonin release during peristalsi…