We have studied the role of three polymorphic genes of the renin-angiotensin system (RAS) as independent risk factors for myocardial infarction (MI) and their correlation with three of the major coronary risk factors: serum cholesterol (CH), hypertension (HT) and smoking (SM). A population of 392 men was genotyped for the M235T polymorphism of the angiotensinogen (AGT) gene, the insertion/deletion of the angiotensin-converting enzyme (ACE) and the all66c of the angiotensin-II type 1 receptor (AT1R), by means of polymerase chain reaction (PCR) and restriction enzyme analysis. It was observed that the T allele frequency increased significantly in the MI with HT, CH, and SM subgroup (0.58 vs 0.31) (p<0.01). In contrast, the M allele frequency was higher in the MI without HT, CH, and SM (0.69 vs 0.42) (p<0.01). A strong association between the MM genotype and MI (p<0.001, odds ratio=4.29, confidence interval=1.95-9.42) was found when age-matched MM control subjects were compared to MI individuals with none of the other known major coronary risk factors. Futhermore, subjects with the MM genotype showed a significantly higher plasma renin activity (PRA) profile than those with the TT genotype (p<0.001). It can be concluded that the M allele is an independent risk factor for MI and the T allele modified the risk when other major risk factors are present.

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In the present study, we studied angiotensin II type 1 (AT1) and type 2 (AT2) receptor messengers by quantitative reverse transcriptase-polymerase chain reaction. We examined peripheral blood mononuclear cells from 30 healthy subjects and 50 subjects with primary hypertension, in whom angiotensin I-converting enzyme genotype was determined, before and after 15 days of treatment with different antihypertensive drugs. The medication included a calcium channel antagonist, an angiotensin I-converting enzyme inhibitor, and a beta 1-blocker. We also studied the relationship between AT1 receptor gene expression and biochemical parameters of the renin-angiotensin system. AT1 receptor messenger levels were positively correlated with plasma renin activity in both normotensive and untreated hypertensive subjects. Increases of this messenger and plasma angiotensin II levels were correlated with the D allele in the same individuals. AT1 receptor messenger levels decreased significantly with angiotensin I-converting enzyme inhibitor treatment in subjects with the DD genotype, and a significant decrease was observed in subjects with the II and ID genotypes treated with a calcium antagonist. No changes were observed in mRNA with the beta 1-blocker. We conclude that the AT2 receptor is not expressed in peripheral leukocytes and that AT1 receptor messenger levels vary in relation to angiotensin I-converting enzyme genotype and pharmacological treatment. These results suggest that angiotensin I-converting enzyme genotype may be an important factor when deciding on antihypertensive therapy in individuals with primary hypertension.

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