Temporal changes in Egr-1 and c-fos expression in rat models of myocardial ischemia

Background The pathological diagnosis of sudden cardiac death caused by myocardial ischemia is a difficult problem. Relevant evidence shows that the expression of Egr-1 and c-fos undergo changes in the early stage of myocardial ischemia, but the detailed temporal variation of them is not clear. Therefore, the aim of this study was to observe the temporal changes in mRNA and protein expression of Egr-1 and c-fos in ischemic myocardium in rats. Methods Sixty-six Sprague-Dawley rats were divided into the control group, the early myocardial ischemia (EMI) group, the sham operated group and the allergy group. The EMI rats were further divided into eight subgroups according to the different time points (30 min and 1, 2, 4, 8, 12, 24, and 48 h) after modeling. The mRNA and protein of Egr-1 and c-fos of each group were detected by real-time quantitative polymerase chain reaction and immunohistochemistry, respectively. Results In the EMI group, Egr-1 mRNA in ischemic myocardium rose 30 min after ischemia and peaked at 2 h; the plateau was maintained up to 8 h after ischemia, and then returned to the baseline level at 12 h. The c-fos mRNA in ischemic myocardium demonstrated a consistent changing curve with that of Egr-1. The mRNA of Egr-1 and c-fos showed no significant changes in the control group, the sham operated group and the allergy group. Immunohistochemistry showed that Egr-1 protein in the myocardial ischemic area was slightly positive 30 min after ischemia, and then strongly positive at 4 and 8 h, decreased at 12 h, and was negative at 24 h. The changing trends of c-fos protein were almost the same as that of Egr-1. Immunohistochemistry of Egr-1 and c-fos protein were all negative in the control group, the sham operated group and the allergy group. Conclusions The mRNA and protein expression of Egr-1 and c-fos presented rapid and temporal changes after myocardial ischemia, and this may be helpful in distinguishing sudden death induced by myocardial ischemia from that of allergy.