AN EXPERIMENTAL MYOCARDIAL-INFARCTION MODEL IN THE RAT AND ITS PROPERTIES

The photochemical reaction between rose bengal and light (540 nm) produces thrombotic occlusion in rat coronary artery. We have now developed an experimental myocardial infarction (MI) model by photochemically induced thrombosis (PIT) in rats and investigated the mechanisms responsible for the induction of MI. PIT in the coronary artery induced myocardial ischemia, which was determined by tissue oxygen tension (tpO(2)), and resulted in MI. Pretreatment with a thromboxane (TX) A(2)-receptor antagonist, vapiprost, prevented a decrease in myocardial tpO(2) and markedly reduced the MI area, although vapiprost inhibited collagen-induced platelet aggregation by 30% ex vivo. An ADP-induced platelet aggregation inhibitor, clopidogrel, also reduced the MI area. In contrast to vapiprost, clopidogrel inhibited collagen-induced platelet aggregation by 90% ex vivo. Pretreatment with a 5-HT2-receptor antagonist, ketanserin, which did not inhibit collagen-induced platelet aggregation ex vivo, prevented the decrease in myocardial tpO(2) and reduced the MI area. These results suggest that TXA(2), 5-HT and ADP play a role in the induction of MI and that platelet aggregation and other factors induce ischemia in this model.