prostaglandin Any of a group of organic compounds derived from essential fatty acids and causing a range of physiological effects in animals. Prostaglandins have been detected in most body tissues. They act at very low concentrations to cause the contraction of smooth muscle; natural and synthetic prostaglandins are used to induce abortion or labour in humans and domestic animals. Two prostaglandin derivatives have antagonistic effects on blood circulation: thromboxane A2 causes blood clotting, while prostacyclin causes blood vessels to dilate. Prostaglandins are also involved in inflammation, being released from affected tissues. See also aspirin.

prostaglandin (pros-tă-gland-in) n. one of a group of hormone-like substances present in a wide variety of tissues and body fluids. Prostaglandins have many actions; for example, they cause contraction of smooth muscle (including that of the uterus) and dilatation of blood vessels, they are mediators in the process of inflammation, and they are involved in the production of mucus in the stomach. Synthetic prostaglandins are used to induce labour or produce abortion and to treat peptic ulcers, glaucoma, and (in newborn babies) congenital heart disease.

prostaglandin One of a group of C₂₀ fatty acids, each containing a five membered ring. Prostaglandins differ from one another in the number and position of double bonds and hydroxyl-group constituents. Their biological effects include the lowering of blood pressure and the stimulation of smooth-muscle contraction.

prostaglandin One of a series of related fatty acids, with hormone-like action, present in semen and liver, brain and other tissues. Their biological effects include the lowering of blood pressure and the stimulation of contraction in a variety of smooth-muscle tissues, such as in the uterus.