Abstract: ObjectiveTo investigate the relationship of the polymorphism of endothelial nitric oxide synthase (eNOS), the 27-bp variable number of tandem repeats (VNTR) in intron 4 with essential hypertension (EH) of the northern Han nationality in China.MethodsGenotypes, the level of plasma nitric oxide metabolites (NOx) and the activity of nitric oxide synthase (NOS) of 207 EH subjects and 231 healthy subjects were measured by polymerase chain-reaction (PCR).ResultsThe frequencies of ecNOS₄a/a,ecNOS₄b/a, and ecNOS₄ b/b in the healthy group were 0.43%, 13.42% and 86.15% respectively. The frequency of the b allele was 92.86%, and the frequency of the a allele was 7.14%. While the frequencies of ecNOS₄ a/a, ecNOS₄ a/b,and ecNOS₄ b/b in the EH group were 0.49%, 19.32% and 80.19% respectively. The frequency of the a allele in EH group (n=42, 10.15%) was significantly higher than that in the healthy group (n=33, 7.14%)(P<0.05). The plasma NOx level of the EH group was 70.04±14.68 mol/L, and significantly lower than that 84.09±27.27 mol/L in the healthy group (P<0.05). Similarly, both the plasma TNOS and iNOS activities of the EH group were 35.49±12.8 U/ml and 14.92±7.93 U/ml, and markedly lower than that 41.47±13.2 U/ml and 10.11±6.21U/ml in the healthy group (P<0.05). But the activities of eNOS in the EH group and healthy group were not significantly different (P>0.05).ConclusionThe variations of ecNOS₄ gene locus may be responsible for the decrement of plasma NOx, both plasma NOx level and activity of NOS decreases in EH patients, so it may be a genetic susceptibility marker for EH of the Han nationality in China.

Key words: hypertension, endothelial nitric oxide synthase (eNOS), DNA polymorphism, gene, nitric oxide(NO)