Abstract: Objective To study the mRNA expression of BNP and c-fos gene in rat heart after acute myocardial ischemia (AMI) and to provide a marker for its medicolegal diagnosis. Methods AMI animal model of rat was made by ligating LAD. mRNA expression of BNP and c-fos gene were studied with RT-qPCR and ordinary PCR at 10 min, 30 min, 60 min and 3 h after the successful ligation. The H&E staining was also used. Changes of the mRNA expression in different time groups were compared. Results There was significant difference in BNP mRNA expression of the 3 h group by RT-qPCR compared with normal control group, 10 min, 30 min, and 60 min groups (P<0.05). There were dramatic differences in c-fos mRNA expression between every two groups (P<0.05) except between the normal group and the 10 min group, between the 30 min group and the 3 h group. The peak of c-fos expression was in 60 min group. No difference was shown between groups by the ordinary PCR. Myocardial fiber acidophilia staining and wavy changes could be seen occasionally at 3 h experimental group by H&E staining. Conclusions C-fos gene probably be used as an auxiliary test for myocardial ischemia of duration of 30 minutes or longer. RT-qPCR may be suitable for diagnosis of early AMI.

Key words: forensic pathology, acute myocardial ischemia, brain natriuretic peptide, c-fos, mRNA