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We hypothesized that angiotensin-converting enzyme (ACE) insertion/deletion polymorphism may be related to arterial phenotypic differences that could explain the adverse effects of deletion polymorphism. Accordingly, contractile responses to angiotensin I and II (0.1 nmol.1(-1)-1 micromol.1(-1), endothelium-dependent relaxation to methacholine (0.01-100 micromol.1(-1), and the effect of NG-monomethyl-L-arginine (L-NMMA; 100 micromol.1(-1) on phenylephrine (10 micromol.1(-1) induced contraction, were studied in isolated rings of internal mammary arteries obtained from patients undergoing coronary bypass surgery. The results were analysed according to the ACE genotype of the patient (II, n = 8; ID, n = 11; DD, n = 9) as well as the presence/absence of either allele. The arteries from patients with the D allele (ID/DD) displayed a lower sensitivity to methacholine (P < 0.05 vs II), which suggested that the capacity of the endothelium for nitric oxide release in response to stimulation was also lower. By contrast, the increase in phenylephrine-induced contraction, by pre-incubation with L-NMMA, was more pronounced in the group with the DD allele (31 +/- 5%) than with the ID (11 +/- 11%) and II alleles (1 +/- 11%, P < 0.05 vs DD), which suggested a higher level of basal nitric oxide release. Finally, the differences in the responses to angiotensin I and II, which were used to evaluate the vascular conversion of angiotensin I, indicated that the level of angiotensin I conversion was higher in patients with the D allele (ID/DD, P < 0.05 vs II). The findings of this study indicate that ACE insertion/deletion polymorphism is related to arterial phenotypic differences in endothelial function and angiotensin I conversion.
Buikema et al. (Wed,) studied this question.