BACKGROUND: A majority scholars views that polymorphism of angiotensinogen T174M gene is one of the susceptible factors of inheritance of coronary heart disease, hypertension and myocardial infarction.OBJECTIVE: To probe into the relationship between the variation of angiotensinogen T174M gene and myocardial infarction.DESIGN: Case-controlled verified experiment.SETTING: Department of Cell Biology, Biochemistry and Molecular Biology, Biological Science Faculty of North China Coal Medical College,and Department of Cardiology in Affiliated Hospital of North China Coal Medical College.PARTICIPANTS: Fifty-five cases of myocardial infarction were collected from outpatients and inpatients in Department of Cardiac Vascular Internal Medicine of Worker's Hospital Affiliated to North China Coal Medical College in Tangshan from September 2002 to September 2003, of which,29 cases were males and 26 cases females, aged (60±8) years. At the same time, 60 cases (health control) were selected from the people who received clinical physical health check (without repeated physical check), of which,32 cases were males and 28 cases females, aged (60±10) years. The cases selected had no manifestation of coronary heart disease, without history myocardial infarction or cerebral infarction in family and the participants were in the know of the research.INTERVENTIONS: Polymerase chain reaction was used to amplify the genetic sequence of No.174 DAN residue involved in No.2 exon of angiotensinogen gene. Electrophoresis was used after variated with Nco I restriction endonuclease.Analysis of restriction fragment length polymorphism was carried on angiotensinogen genotype. Simultaneously,the relevant risk factors of coronary heart disease were detected in two groups, such as blood pressure, body mass, blood lipid, fasting blood glucose, etc.MAIN OUTCOME MEASURES: ① Distribution of genotype, frequency of genotype and frequency of allele in two groups. ② Analysis on risk factors of two groups.RESULTS: Totally 115 cases of objects all accomplished the design and entered result analysis. ① Frequency of angiotensinogen genotype: in myocardial infarction group, TT 75％ (41/55), TM 18％ (10/55), MM 7％ (4/55) and in control group, TT 83％ (50/60), TM 15％ (9/60), MM 2％ (1/60). Frequency of allele of M174 and T174 were 16％ (18/110), 84％ (92/110) and 9％ (11/120), 91％ (109/120) in myocardial infarction group and control group respectively. Frequency of allele of M174 in myocardial infarction group was significantly higher than that of control group (x2=5.79,P ＜ 0.05). By the division of sex, the frequency M and T alleles of both male and female in experiment group was basically identical to control group. Angiotensinogen 174MM genotype in myocardial infarction group was significantly higher than control group (x2= 7.55, P ＜ 0.025). ② Comparison of risk factors: The percentage of smoking history in myocardial infarction group was significantly higher than control group (P = 0.006). After correction of essential risk factors of coronary heart disease, angiotensinogen 174MM gene still increased significantly the risk of myocardial infarction (Odds ratio was 3.66, P= 0.018).CONCLUSION: Angiotensinogen genotype is related to the occurrence of myocardial infarction. M allele is one of the susceptible factors of inheritance of myocardial infarction and T allele prevents from myocardial infarction. The attack of myocardial infarction is not relevant to sex, but angiotensinogen 174TM gene is one of the essential risk factors of myocardial infarction.