Background: The renin-angiotensin system is involved in blood pressure regulation. The insertion/deletion (I/D) polymorphism of the angiotensin-converting enzyme (ACE) gene is known to be associated with variation of plasma and cellular ACE concentrations. Furthermore, changes in arterial function have been suggested to be associated to the DD genotype. The aim of the study was to investigate the arterial vascular response to a physiologic stimulus (i.e., flow) according to the I/D ACE gene polymorphism.
Methods: Sixty patients scheduled for coronary artery bypass grafting (n = 24) or valve surgery (n = 36) under normothermic cardiopulmonary bypass were genotyped in a blind manner by polymerase chain reaction. Mean arterial pressure was measured at pump flows ranging from 1 to 3 l x min(-1) x m (-2) by 0.25 l x min(-1) x m(-2) step each 15 s, to obtain a pressure-flow relation. Independent factors associated with the variation of the slope of the pressure-flow relation curve were assessed by multivariate analysis.
Results: We found a D allelic frequency of 0.54. Patients were separated in two groups (DD, n = 16; ID/II, n = 44). There were no significant difference with regard to preoperative and intraoperative data between the two groups. DD patients had their pressure-flow relation curves shifted upward (with higher pressures as flow increased), indicating a lesser decrease in vascular resistance. Furthermore, DD genotype was the only independent predictor of the slope of the curves (21.5 +/- 4.2 vs. 18.1 +/- 5 mmHg/[l x min(-1) x m(-2)] for DD and ID/II, respectively; P = 0.02; values are mean +/-SD).
Conclusion: These results show that vasomotor properties are influenced by the I/D polymorphism of the ACE gene.