5-Hydroxytryptamine mast cells

Although it appears that severe IL-4-regulated enteropathy is not required for immune expulsion of T. spiralis, it is still possible that Th2 cytokines can act in a direct fashion to create an environment unfavourable for intestinal parasites. It remains to be shown directly whether these effects are sufficient to expel parasites. Indeed, there is considerable evidence to support a variety of pathophysiological effects of IL-4 and/or TNF on the gut. These effects may be mediated by factors including cytokines and mast-cell products (e.g. leukotrienes and 5-hydroxytryptamine). 7. spiralis infections result in increased fluid and mucus secretion into the lumen as well as increased intestinal propulsive activity and more rapid intestinal transit (Castro et al, 1979 Russell, 1986 Vermillion and Collins, 1988 Vermillion et al., 1991 Weisbrodt et al, 1994 Barbara et al, 1997). The increased contractility of radial and longitudinal muscle is greater in high-... 

Figure 17.37 Hay fever. Pollen grains bind to sensib sed mast cells which degranulate, releasing the active biochemicals that result in the allergic response. Serotonin is 5-hydroxytryptamine.

They are mediated by IgE antibodies. On exposure to the drug, antigen and antibody reaction takes place on mast cells and basophils releasing various mediators e.g. histamine, leukotrienes, 5 hydroxytryptamine (5-HT), prostaglandins etc., which are responsible for immediate immune reactions like skin reaction, anaphylactic shock, asthma etc. These reactions occur immediately after challenge and are termed as immediate hypersensitivity. 

Hydroxytryptamine is widely distributed in plant and animal tissues, mast cells, platelets, the enterochromaffin cells located throughout the gastrointestinal tract, and in certain regions of the brain. It is also present in the venoms and stings. Some fruits such as bananas, pineapples, tomatoes and plums contain considerable amount of 5-HT. 

Tryptophan appears to be converted to a larger number of metabolites than any of the other amino acids. The degradation of tryptophan in animals occurs mainly in two pathways, I and II (Figure 4.1). The first major pathway (I), initiated by the action of tryptophan dioxygenase, involves oxidation of tryptophan to N - fc > r my I ky n urenine and the formation of a series of intermediates and byproducts, most of which appear in varying amounts in the urine, the sum of which accounts for the total metabolism of tryptophan, approximately. The second pathway (II) involves hydroxylation of tryptophan to 5-hydroxytryptophan and decarboxylation of this compound to 5-hydroxytryptamine (serotonin), a potent vasoconstrictor found particularly in the brain, intestinal tissues, blood platelets, and mast cells. A small percentage (3%) of dietary tryptophan is metabolized via the pathway (III) to indoleacetic acid. Other minor pathways also exist in animal tissues. 

Serotonin S-hydroxytryptamine, M, 176.2, a plant and animal hormone. It is produced by hydroxylation of L-tryptophan to 5-hydroxytryptophan, followed by decarboxylation. The synthesis occurs in the central nervous system, lung, spleen and argentaffine light cells of the intestinal mucosa. S. is stored in thrombocytes and mast cells of the blood. It acts as a Neuro-transmitter (see), stimulates peristalsis of the intestine, and causes a dose-dependent constriction of smooth muscle. It stimulates the release from arterial endothelium of a dilator substance which counteracts its primary constricting effect [T.M. Cocks X A. Angus Nature 305 (1983) 627-630]. S. is a precursor of the hormone Melatonin (see). It is inactivated and degraded by monoamine oxidases and aldehyde oxidases to 5-hydroxy-indoleacetic acid. 

D. A. Rowley and E. P. Benditt, 5-Hydroxytryptamine and Histamine as Mediators of the Vascular Injury Produced by Agents Which Damage Mast Cells in Rats, J. exp. Med. 103, 399-412 (1956). 

G.B.West, 5-Hydroxytryptamine, Tissue Mast Cells and Skin Oedema, Int. Archs Allergy appl. Immun. 10, 257-275 (1957). 

West, G. B., 5-Hydroxytryptamine, tissue mast cells and skin oedema. Internal. Arch. Allergy 10, 257 (1957). 

Rowley, D. A. and Benditt, E. P., 5-Hydroxytryptamine and histamine as mediators of the vascular injury produced by agents which damage mast cells in rats, J. Exp. Med. 103, 399 (1956). 

Although the most common and characteristic type of connective tissue cell is the fibroblast many other types of cell are present in loose connective tissue. These mostly have a protective role. They include fat cells, macrophages, plasma cells, mast cells and leucocytes. The macrophages and some of the leucocytes are phagocytic and are able to engulf cellular debris, bacteria and inert foreign matter the plasma cells are derived from B-lymphocytes and produce immunoglobuUns while the mast cells produce heparin and histamine and also, in some species, serotonin (5-hydroxytryptamine). 

R.M. Williams, J.B. Shear, WR. Zipfel, S. Maiti, W.W. Webb, Mucosal mast cell secretion processes imaged using three-photon microscopy of 5-hydroxytryptamine autofluorescence. Biophys. J. 76, 1835-1846 (1999)... 

Carbon fibre microelectrode A 1.4 pM Determination of histamine and 5-hydroxytryptamine in isolated mast cells 125... 

Pihel K, Hsieh S, Jorgenson JW, Wightman RM (1995) Electrochemical detection of histamine and 5-hydroxytryptamine at isolated mast cells. Anal Chem 67 4514—4521... 

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