BACKGROUND: Endothelial nitric oxide synthase (eNOS) as well as nitric oxide play an important role in the regulation of cardiovascular function. There are limited and controversial data regarding the impact of polymorphisms of eNOS gene that is implicated in the vasoconstrictive properties of the endothelium in the pathogenesis of premature myocardial infarction (MI).OBJECTIVE: We examined whether two common polymorphisms of eNOS gene (G894T and T786C) are associated with the development of premature MI.METHODS: We recruited 107 patients with premature MI and compared them to 103 age- and sex- matched controls. All patients underwent coronary angiogram and were classified into the subgroup of patients with ‘normal’ or ‘near normal’ coronary arteries and the subgroup of patients with significant coronary artery disease (≥ 50% stenosis in lumen diameter of coronary arteries). The genetic polymorphisms of eNOS gene were assayed with polymerase chain reaction and reverse hybridization.RESULTS: Nineteen patients (17.8%) had ‘normal’ or ‘near normal’ coronary arteries. A significantly higher frequency of homozygosity for the 786C (32%) and the 894T (21%) alleles of the eNOS gene in patients who develop early MI in the setting of angiographically 'normal' or 'near normal' coronary arteries were found.CONCLUSIONS: Our data suggest that the T786C and the G894T genetic polymorphisms are associated with the development of MI in very young individuals, whose coronary arteries are characterized by very small atheromatic burden.