A preliminary study on T-786C endothelial nitric oxide synthase gene and renal hemodynamic and blood pressure responses to dietary sodium

The purpose of the present study was to examine the role of the T-786C endothelial nitric oxide synthase (eNOS) gene polymorphism on changes in renal hemodynamics and blood pressure due to Na⁺ loading. Twenty-eight older (63±1 years), moderately obese (39±2 % fat) hypertensives had their glomerular filtration rate (GFR), renal plasma flow (RPF), blood pressure (BP) and plasma nitric oxide (NO_x) levels determined after eight days of low (20 mEq) and high (200 mEq) Na⁺ diets. The two Na⁺ diets were separated by a 1-week washout period. Subjects were genotyped for the eNOS-786 site and were grouped on whether they were homozygous or heterozygous for the C allele (TC+CC, n=13) or only homozygous for the T allele (TT, n=15). The TC+CC genotype group had a significantly greater increase in diastolic (P=0.021) and mean arterial (P=0.018) BP and a significant decline in both RPF (P=0.007) and GFR (P=0.029) compared to the TT genotype group with Na⁺ loading. Furthermore, Na⁺ loading resulted in a significant (P=0.036) increase in plasma NO_x in the TT, but not in the TC+CC genotype group as well as a trend (P=0.051) for an increase in urine NO_x in TC+CC, but not in the TT genotype group. The increase in BP during Na⁺ loading in older hypertensives was associated with the eNOS genotype and may be related to changes in renal hemodynamics due to changes in NO metabolism.