Polymorphisms of the endothelin-A and -B receptor genes in relation to blood pressure and myocardial infarction : The etude cas-témoins sur l’infarctus du myocarde (ECTIM) study

Endothelin-1 is a potent vasoconstrictor that has also mitogenic properties, stimulating the synthesis and secretion of several vasoactive molecules. There is much evidence to suggest that endothelin-1 might be involved in the pathogenesis of hypertension, atherosclerosis, and ischemic heart disease. Endothelin-1 exerts its effects through at least two receptors, ETA and ETB, which are encoded by different genes and have separate tissue distributions and biologic properties. The objective of this study was to identify polymorphisms of the ETA and ETB receptor genes and to study their association with myocardial infarction (MI) and blood pressure. The coding regions and 1.3 kb upstream of the ETA and ETB receptor genes were explored by polymerase chain reaction/single strand conformation polymorphism. Six polymorphisms were found in the ETA receptor gene and three in the ETB receptor gene. Most of these polymorphisms were frequent. Associations between the detected polymorphisms, blood pressure, and MI were examined in the ECTIM study, a multicenter study comparing 652 patients having survived an MI and 773 controls from Belfast (Northern Ireland) and France. Alleles at the different polymorphic sites were similarly distributed in patients with MI and controls. Allele frequencies were similar in both countries, except for the ETA/−231 G allele, which appeared more frequently in France than in Belfast (P< .01). The mean systolic and diastolic blood pressure levels did not significantly differ between genotypes. However, a C/T substitution located in the nontranslated part of exon 8 of the ETA receptor gene (ETA/EX8nt1363) was associated with pulse pressure (P< .005). These results do not support an involvement of the endothelin receptor genes in a predisposition to MI or the determination of blood pressure levels, but suggest that a polymorphism of the ETA receptor gene might influence the pulse pressure. This result will have to be confirmed in other studies.