抄録
Myocardial infarction was induced in rats by ligation of left coronary descending artery and ischemic injury was followed up to 48hr. After the ligation, blood flow resumed into ischemic area from surrounding normal tissue, as known by intensely staining of the marginal zone of the ischemic area with pontamine sky blue, which was injected intravenously one hour before cardiac arrest at each time. Infarct size, evaluated by unstained area of triphenyltetrazolium chloride, reached a plateau at 12hr. Neutrophils were also accumulated from 3hr and then increased extensively from 12 to 24hr. The LTB4 content in the cardiac tissue was also increased 4 times at 3hr, compared with that in sham operated controls. Single oral administration of a 5-lipoxygenase inhibitor (AA-861) (80mg/kg) one hr before ligation decreased the LTB4 content to the control and the neutrophil count at 3hr by 40%. Furthermore, the infarct size at 48hr was also suppressed by AA-861 by 34%. Single oral administration of the inhibitor at 2, 8 or 24hr after ligation also suppressed the infarct size by 18, 19 or 19% respectively. These results clearly indicate tht LTB4 was generated in the ischemic cardiac tissue, attracted neutrophils and indirectly enhanced the exacerbration of the infarct size.
