Changes of the plasma atrial natriuretic peptide during myocardial infarction in rats

Atrial natriuretic peptide (ANP) is associated with the variety of disorders of myocardial function. The effect, however, of myocardial infarction (MI) on ANP has not been fully described. Thus, this study investigated the effect of experimental MI, induced by left coronary artery ligation, on ANP secretion. Male Sprague-Dawley rats aged 60 d underwent ligation of the left anterior descending coronary artery to induce MI and were compared with a group that underwent a sham operation. Rats of sham operation had a similar procedure without having the suture tightened around the coronary artery. Animals were sacrificed at 1, 3, 6, 12, and 18 h or 1, 3, 5, 7, 14, and 30 d after the procedure. MI size was assessed by planimetry and perimetry, and plasma ANP levels were determined by radioimmunoassay. Mean infarct size was 39.6-44.5% of the left ventricle after coronary occlusion in experimental groups. No significant differences were observed in infarct size among groups. In contrast, the concentration of plasma ANP was significantly higher at 1,3, 6, 12, 18, and 24 h after left coronary artery ligation than in sham animals. This parameter, however, did not differ significantly at 3, 5, 7, 14, and 30 d after ligation compared with sham-ligated controls. These results demonstrate that plasma ANP levels are markedly increased in the early phase of MI in the male rat and can be a useful biomarker for diagnosis in acute MI.