Prostaglandins
Prostaglandin is one of the prostanoid class of fatty acid derivative lipids containing prostaglandins and thromboxanes. The prostanoid class is a subclass of eicosanoids. They are mediators and have a variety of strong physiological effects.
The name prostaglandin comes from the prostate gland. When prostaglandin was first isolated from seminal fluid in 1936, it was believed to have been added from the prostate.
Prostaglandins are found in many human tissues and organs. They are synthesized in cell membranes from arachidonate acid created by phospholipase A2, the intermediate is then passed into one of either the cyclooxygenase or lipoxygenase pathways to form either prostaglandin and thromboxane or leukotriene. The cyclooxygenase pathway produces thromboxane, prostacyclin and prostaglandin D, E and F. The lipoxygenase pathway is active in leukocytes and in macrophages and synthesises leukotrines.
Prostaglandins have a wide variety of actions but most cause muscular constriction and inflammation. Other effects can be calcium movement, hormone regulation and cell growth control. Thromboxane is created in platelets and causes vasular constriction and platelet aggregation. Prostacyclin comes from cells in the blood vessel walls and is antagonistic to thromboxane.
Prostaglandins are potent but only active for a short time before being inactivated and excreted.
NSAIDs inhibit cyclooxygenase and reduce prostaglandin sysnthesis. Corticosteroids inhibit phospholipase A2 production by boosting production of lipocortin, an inhibitor protein.
Synthetic prostaglandins are used to induce labour (E2 or F2, with mifepristone), to treat gastric or duodenal ulcers (E), and in the treatment of newborn babies with heart disease (to close the ductus arteriosus)
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