Effect of tryptophan administration on circulating melatonin levels in chicks and rats: Evidence for stimulation of melatonin synthesis and release in the gastrointestinal tract

The aim of the present study was to test the hypothesis that 3,4-dihydroxyphenylalanine (DOPA) and dopamine (DA) in the gastrointestinal tract are to a large extent of exogenous origin and derived from food. Tissue concentrations of norepinephrine (NE), epinephrine (Epi), DA, DOPA, and 3,4-dihydroxyphenylacetic acid (DOPAC), as measured by reverse-phase HPLC with electrochemical detection, were studied in fed and 4-day-fasted Wistar rats as well as in sympathectomized and adrenodemedullated rats. Sympathectomy and adrenal demedullectomy decreased tissue concentrations of NE and Epi, respectively, but had no effect on the level of tissue DOPA. Large amounts of DOPA and DA were present in the gastrointestinal tract. Fasting decreased DOPA and DA in the stomach and DOPA concentrations in the quadriceps muscle but no concentrations in other organs. DOPAC in the heart decreased both in response to sympathectomy and to fasting, whereas DOPAC decreased in plasma after fasting and in skeletal muscle after sympathectomy. We conclude that the food content of DOPA and DA is of major importance for the metabolism of DA and, thus, for the dopamine-sulfate content in the gastrointestinal tract and in plasma. The decrease in muscle DOPA after fasting may be explained by less insulin being available during fasting for stimulation of DOPA uptake in the muscle depot. DOPAC in the organism seems to be of a dual origin, derived partly from DA in the food and partly from DA synthesized in sympathetic nerves.

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Nonadrenergic inhibitory nervous system in human airways

Journal of Applied Physiology ◽

10.1152/jappl.1976.41.5.764 ◽

1976 ◽

Vol 41 (5) ◽

pp. 764-771 ◽

Cited By ~ 234

Author(s):

J. Richardson ◽

J. Beland

Keyword(s):

Smooth Muscle ◽

Gastrointestinal Tract ◽

Electrical Field Stimulation ◽

Field Stimulation ◽

Inhibitory System ◽

Electrical Field ◽

Human Airways ◽

Adrenergic Blocking ◽

Stimulation Of

Human airways, from the middle of the trachea to the distal bronchi, were studied in vitro for the presence of inhibitory nerves. The tissue was obtained from operations and from recent autopsies. Electrical field stimulation of the tissues demonstrated cholinergic, excitatory nerves and their effect was blocked by atropine. Field stimulation of the tissues, in the presence of atropine, relaxed the smooth muscle even when the muscle was contracted by histamine. The field stimulation-induced relaxation was neither blocked nor modified by adrenergic blocking agents. Maximum relaxation of the bronchial muscle was obtained with a pulse duration of 1–2 ms, 70 V,and frequencies of 20 Hz and greater. The tracheal smooth muscle showed 85%of maximal relaxation with a frequency of 10 Hz. Tetrodotoxin, blocked the field stimulation-induced relaxation for pulse durations of 2 ms; this indicated that nerves were being stimulated. The airway system shows some of the characteristics of the nonadrenergic inhibitory system in the gastrointestinal tract and of the system reported in the guinea pig trachealis muscle.No evidence of adrenergic inhibitory fibers was found in the bronchial muscle with either pharmacological or histochemical techniques. These findings suggest that the nonadrenergic inhibitory system is the principal inhibitory system for the smooth muscle of human airways. We suggest that a defect in the airway system, such as that shown in the gastrointestinal tract, may be an explanation for the hyperreactive airways of asthma and chronic bronchitis.

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Involvement of 5-Lipoxygenase Pathway in Norepinephrine Stimulation of Rat Pineal Melatonin Synthesis

Neuroendocrinology ◽

10.1159/000124854 ◽

1987 ◽

Vol 46 (5) ◽

pp. 412-416 ◽

Cited By ~ 12

Author(s):

Maria I. Vacas ◽

Maria I. Keller-Sarmiento ◽

Graciela S. Etchegoyen ◽

Elba N. Pereyra ◽

Martha F. Gimeno ◽

...

Keyword(s):

Lipoxygenase Pathway ◽

Pineal Melatonin ◽

Melatonin Synthesis ◽

Stimulation Of

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Monochloramine induces reorganization of nuclear speckles and phosphorylation of SRp30 in human colonic epithelial cells: role of protein kinase C

AJP Cell Physiology ◽

10.1152/ajpcell.00090.2003 ◽

2003 ◽

Vol 285 (5) ◽

pp. C1294-C1303 ◽

Cited By ~ 8

Author(s):

Ya-Qin Zhu ◽

Yu Lu ◽

Xiao-Di Tan

Keyword(s):

Gastrointestinal Tract ◽

Epithelial Cells ◽

Intestinal Epithelial Cells ◽

Morphological Changes ◽

Sr Proteins ◽

Mrna Splicing ◽

Intestinal Epithelial ◽

Nuclear Speckles ◽

Colonic Epithelial Cells ◽

Stimulation Of

Intestinal epithelial cells are constantly stimulated by reactive oxidant metabolites (ROMs) in inflamed mucosa. Monochloramine (NH2Cl), a cell-permeant ROM, is particularly relevant to the pathogenesis of inflammation in the gastrointestinal tract. Nuclear speckles, a unique nuclear subcompartment, accumulate a family of proteins, namely, serine- and arginine-rich (SR) proteins. They play important roles in regulation of pre-mRNA splicing. Currently, little is known about the link between inflammatory stimulation and the pre-mRNA splicing process, although gene expression is changed in inflamed tissues. The present study was designed to investigate whether stimulation of human colonic epithelial cells (HT-29 and Caco-2 cell lines) with NH2Cl affects nuclear speckles and their components. By indirect immunofluorescence, nuclear speckles have been shown to undergo rapid aggregation after NH2Cl stimulation. By utilizing Western blotting, SRp30 (a subset of SR proteins) in intestinal epithelial cells was found to be phosphorylated after NH2Cl treatment, whereas other SR proteins were not responsive to NH2Cl stimulation. The cytotoxic effect of NH2Cl was excluded by both negative lactate dehydrogenase assay and propidium iodide staining. Therefore, NH2Cl-induced morphological changes on nuclear speckles and phosphorylated SRp30 do not result from intestinal epithelial injury. Furthermore, the effect of NH2Cl on nuclear speckles and SRp30 was blocked by bisindolylmaleimide I, a selective PKC inhibitor. Together, the available data suggest that stimulation of intestinal epithelial cells with NH2Cl results in a consequent change on pre-mRNA splicing machinery via a distinctive signal pathway involving activation of PKC. This effect may contribute to oxidant-induced pathophysiological changes in the gastrointestinal tract.

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Distribution and function of enteric GAL-IR nerves in dogs: comparison with VIP

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.1989.256.5.g884 ◽

1989 ◽

Vol 256 (5) ◽

pp. G884-G896 ◽

Cited By ~ 5

Author(s):

T. Gonda ◽

E. E. Daniel ◽

T. J. McDonald ◽

J. E. Fox ◽

B. D. Brooks ◽

...

Keyword(s):

Smooth Muscle ◽

Small Intestine ◽

Gastrointestinal Tract ◽

Vasoactive Intestinal Polypeptide ◽

Myenteric Plexus ◽

Low Doses ◽

Field Stimulation ◽

And Function ◽

Higher Doses ◽

Stimulation Of

The distribution of nerves containing galanin-immunoreactive (GAL-IR) material was compared to the distribution of neurons containing vasoactive intestinal polypeptide (VIP) immunoreactivity in the canine gastrointestinal tract. The actions of intra-arterially administered galanin and VIP on motility in the gastric antrum and corpus and the intestines were also studied. All sphincter muscles contained galanin- and VIP-immunoreactive nerve profiles. VIP-immunoreactive nerve profiles were present in all layers of the stomach, small intestine, and colon. GAL-IR nerve somata were common in the submucous plexus of ileum and colon and in the myenteric plexus of the terminal antrum, as were nerve processes in various layers. In the small intestine, galanin inhibited contractile responses to field stimulation of intrinsic nerves and also reduced the contractions after nerve blockade with tetrodotoxin (TTX). VIP often enhanced field-stimulated contractions at low doses but inhibited these and the contractions after TTX at higher doses. In the stomach and colon, both peptides inhibited responses to field stimulation; whether these effects were due to actions on smooth muscle was not tested. The distribution and actions of galanin in gut are consistent with the hypothesis that it acts at smooth muscle sites and possibly at prejunctional sites.

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