[Prostaglandins and leukotrienes].

Two classes of arachidonic acid derivatives can be formed by two distinct enzyme systems. Cyclo-oxygenases synthesise prostaglandins, prostacyclin and thromboxane A2 which all possess both pro- and anti-inflammatory properties. Lipoxygenases synthesise on the one hand chemotactic factors, the hydroxylated derivatives of arachidonic acid, the most powerful of which is leukotriene B4, and on the other hand the broncho-constricting and permeability-increasing factors, leukotrienes C4, D4 and E4. A variety of pharmacological agents can decrease the formation of these compounds or inhibit their actions.