CARDIAC ULTRASTRUCTURAL EFFECTS OF THE PLATELET-ACTIVATING-FACTOR ANDITS ANTAGONIST BN-52021

Platelet-activating factor-induced ultrastructural changes of myocardi um were examined in isolated perfused guineapig heart. The platelet-ac tivating factor (10(-9)-10(-7) M) caused the following electron micros copic changes: a) dilated capillaries filled with platelets and aggreg ated 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 de nsity and rupture of crest in mitochondria can be seen. c) Ca2+ deposi ts in the cytoplasm increased and appeared in mitochondria, too.d) the intramitochondrially localised cytochromoxydase and succinic dehydrog enase activities were decreased. e) using lanthanum tracer permeabilit y alterations were observed. Pretreatment with BN 52021 (10(-6) M) com pletely prevented the morphological effects of the platelet-activating factor. From these results we conclude that the platelet-activating f actor-induced vascular and ischemic like cellular damage appears to pl ay an important role in the pathophysiology of myocardial ischemia.