Leukotriene
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Leukotrienes are autocrine and paracrine eicosanoid lipid mediators derived from arachidonic acid by 5-lipoxygenase.
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History and name
The name leukotriene comes from the words leukocyte and triene (a compound with three double bonds). What would be later named leukotriene C, "slow reaction smooth muscle-stimulating substance" (SRS) was originally described in 1938 by Feldberg and Kellaway. The researchers isolated SRS from lung tissue after a prolonged period following exposure to snake venom and histamine.
Biochemistry
Synthesis
Leukotrienes are synthesized in the cell from arachidonic acid by 5-lipoxygenase. The lipoxygenase pathway is active in leukocytes and in macrophages and synthesizes leukotrines.
Function
Leukotrienes act principally on a subfamily of G protein coupled receptors. They may also act upon peroxisome proliferator-activated receptors. Leukotrienes are involved in asthmatic and allergic reactions and act to sustain inflammatory reactions; several leukotriene antagonists are used to treat asthma.
Leukotrienes, are vey important agents in the inflammatory response. Some such as LTB4 have a chemotactic effect on migrating neutrophils, and as such help to bring the necessary cells to the tissue. Leukotrienes also have a powerful effect in vasoconstriction particularly of venules and of bronchoconstriction, they also increase vascular permeability. Examples of leukotrienes are LTB4 LTC4 LTD4 and LTE4.