[Biology of prostaglandins with reference to therapeutic aspects]

Prostaglandins are highly potent derivatives of unsaturated fatty acids with multiple biological activities. They are synthesized and metabolized in almost all tissues studied so far. The E- und F-type prostaglandins may be regarded as local modulators of hormonal effects on cell function and--in some cases (kidney, uterus-corpus luteum)--as regional or tissue hormones. Thus they seem to be involved in the regulation of neurotransmission, kidney function, triglyceride metabolism in adipose tissue and progesterone biosynthesis. Apart from their influence on renal blood flow prostaglandins of the A-type possibly have an additional function as circulatory hormones regulating blood pressure. Second messenger-systems (cAMP, Ca++-cGMP) which mediate the effects of most non-steroidal hormones are also involved in the action of prostaglandins, at least of the E-and F-types. Disturbances in prostaglandin metabolism (increased or decreased biosynthesis) are discussed to play a role in the pathogenesis of inflammation, pain, fever, hypertension, bronchial asthma and gastric or duodenal ulcer formation. Drugs with antiinflammatory, analgesic and antipyretic activity have been shown to be potent inhibitors of prostaglandin formation. The correlation of a local prostaglandin deficit or the therapeutic use of single effects of prostaglandins by administration of exogenous compounds (natural prostaglandins or modified derivatives) has so long been less satisfactory because of their large number of biological actions which lead to undesired side effects. Extensive experience have been obtained in the successful induction of therapeutic abortion. This effect is based on the stimulatory action of E- and F-type prostaglandins on the smooth muscles of the pregnant uterus which is resistent to the influence of other stimuli, e. g. oxytocin. Here the incidence of side effects could be reduced by local administration of low doses of prostaglandins into the uterine cavity. A general improvement of the therapeutic usefulness of prostaglandins will however only be achieved, if modified derivatives with more specific actions on the desired "target" tissues are available.