Endothelial nitric oxide synthase gene haplotypes affect nitrite levels in black subjects.

Polymorphisms in the endothelial nitric oxide synthase (eNOS) gene have been associated with variations in nitric oxide (NO) formation and response to drugs in white subjects. We examined whether genetic polymorphisms (T-786C, b/a intron 4 and Glu298Asp) and haplotypes of the eNOS gene affect NO formation in 179 healthy black subjects. To assess NO formation, we measured the concentrations of nitrite in the plasma, red blood cells and whole blood. Although we found no effects of individual eNOS polymorphisms on NO formation, we found that the 'C-4b-Glu' haplotype is significantly more common in subjects with low circulating plasma and whole blood nitrite concentrations compared with subjects with high circulating nitrite concentrations (both P<0.0007). These findings reproduce previous findings in white subjects and are consistent with the idea that defining genetic markers is more important than ethnic classification, at least in terms of NO formation.