[The role of platelet activating factor in the pathogenesis of asthma].

The work reviews knowledge about the function of PAF, the presupposed mediator of asthma. The PAF mediator evokes contraction of smooth muscles of respiratory passages, too in vivo as in vitro, by means of an indirect mechanism involving activated platelets which function as intermediaries. The constrictor released due to this process can be represented by histamine or a product of arachidonic acid. Mucous secretion is according to current knowledge stimulated by PAF. The PAF mediator appears to be a considerable chemotactic factor for eosinophils which by their cytotoxic effects on respiratory epithelium support the origin and development of bronchial hyperresponsiveness. PAF has an eminent effect on the growth of microvascular permeability. Antagonists of PAF inhibit some mentioned PAF effects. Their possible therapeutic utilization, excluding ketotiphen, are currently subjected to research. (Fig. 2, Ref. 17.).