Cardiac ultrastructural effects of the platelet-activating factor and its antagonist BN 52021

Abstract

Platelet-activating factor-induced ultrastructural changes of myocardium were examined in isolated perfused guinea pig heart. The platelet-activating factor (10(-9)-10(7) M) caused the following electron microscopic changes: a) dilated capillaries filled with platelets and aggregated platelets. The endothelial cells adjoining the platelets remained uninjured but pericapillary oedema was observed. b) in the myocardium intracellular oedema, myofibrillar alterations, decrease of matrix density and rupture of crest in mitochondria can be seen. c) Ca2+ deposits in the cytoplasm increased and appeared in mitochondria, too. d) the intramitochondrially localised cytochromoxydase and succinic dehydrogenase activities were decreased. e) using lanthanum tracer permeability alterations were observed. Pretreatment with BN 52021 (10(6) M) completely prevented the morphological effects of the platelet-activating factor. From these results we conclude that the platelet-activating factor-induced vascular and ischemic like cellular damage appear to play an important role in the pathophysiology of myocardial ischemia.