Mast cells storage

Mast Cells and Basophils. The chief sites of histamine storage are mast cells in the tissues and basophils in blood. These cells synthesize histamine and store it in secretory granules along with a heparin-protein complex. In response to specific antigens, mast cells or basophils are sensitized. Histamine is then secreted from the storage granules. Besides the histamine stores in mast cells and basophils, there is evidence of non-mast cell histamine in some tissues, particularly gastric and intestinal mucosa (60). 

Virtually all of the histamine found in individual organs and tissues is synthesized locally and stored in sub cellular secretory granules. Within the tissues, the mast cells are the principal sites of storage in the blood, the ba-... 

Drugs, particularly organic bases, may release histamine from mast cells by physically displacing the amine from its storage sites. Morphine, codeine, d-tubocu-rarine, guanethidine, and radiocontrast media can release histamine from mast cells. Basic polypeptides, such as bradykinin, neurotensin, substance P, somatostatin, polymyxin B, and the anaphylatoxins resulting from complement activation, also stimulate histamine release. Venoms often contain basic polypeptides as well as the histamine-releasing enzyme phospholipase A. 

Histamine metabolism differs from that of classical neurotransmitters because histamine is so widely distributed in the body. The highest concentrations in human tissues are found in the lung, stomach, and skin (upto 33 ug/g tissue). Histamine metabolic pathways are simple histamine is produced from histidine in just one step (see figure 4.11). The principal production takes place in the mast cells of the peritoneal cavity and connective tissues. The gastric mucosa is another major storage tissue. Histamine can be found in the brain as well. 

Lack of histamine-immunoreactive mast cells suggests that the observed changes occur in the neuronal pool. Obviously, the postmortem time and storage... 

By preventing the release of histamine from storage cells glucocorticoids and sodium cromoglicate can suppress IgE-induced release from mast cells. Pj-agonists have a similar effect. 

Anticoagulant, storage matrix for mast cell mediators, fibroblast activation, protects growth factors from degradation and potentiates their action, endothelial cell migration... 

It is now many years since it was discovered that heparin is a constituent of the mast cell granule. Because it has been found in mast cells, many assume that this cell is the principal site of synthesis of this polysaccharide. However, there is evidence also that fibroblasts not only make hyaluronic acid, but possibly sulfated chondroitin polysaccharides as well. - There is not always a distinct correlation between the numbers of mast cells and the content of heparin of a particular tissue. The mast cell is found only in connective and reticular tissues. There is some evidence that mast cells in culture may synthesize heparin.However, another point of view has been put forward that the fibroblasts may make the polysaccharide and store it for a time and that, when they are full of these storage granules, they are called mast cells. ... 

Mast cells may disrupt (clasmatosis) and release their granules into the ground substance, liberating heparin and other chondroitin sulfates. Thus, the mast cell may be a storage form of the fibroblast. This release of granules is similar to secretion of many substances by other cells and would be a merocrine type of secretory activity. 

The histamine release in the brain, and perhaps other sites, involves exocytosis, as this potassium-induced release is a calcium-dependent process. Histamine is released by many factors. For example, histamine is released by numer-ons drugs including reserpine, codeine, meperidine, hydralazine, morphine, d-tnbocurarine, dextrans, papaverine, and compound 48/80. However, the different histamine storage sites show certain degrees of specificity. For example, the histamine in mast cells is not released following potassium-induced depolarization or by reserpine, factors that release histamine from nenrons. Conversely, compound 48/80, which releases histamine from mast cells, is not able to release histamine from nenrons. 

The specific histidine decarboxylase of mast cells apparently produces histamine for local storage within the mast cell itself. This may be the primary function of the mast celP . 

Almost all mammalian tissues contain histamine in amounts ranging from <1 to >1(X) pg/g. Concentrations in plasma and other body fluids generally are very low, but human cerebrospinal fluid (CSF) contains significant amounts. The mast cell is the predominant storage site for histamine in most tissues in the blood, it is the basophil. The concentration of histamine is particularly high in tissues that contain large numbers of mast cells, such as skin, bronchial tree mucosa, and intestinal mucosa. 

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