背景　高血壓患者有遺傳傾向且其血管內皮細胞產生的一氣化氮(nitric oxide; NO)有減少的現象。吾人假設具有894G>T內皮一氣化氮合成?(endothelial NO synthase; eNOS)基因多型態(polymorphism)的原發性高血壓患者會影響其血管內皮合成一氧化氮，因而和患者之晝夜血壓變化有關。方法　本研究選取101位原發性高血壓患者，所有受試者均接受二十四小時血壓紀錄及eNOS之894G>T多型態檢驗。參與研究之高血壓患者依其二十四小時血壓紀錄分為四類型：夜間血壓下降極明顯者(extreme dippers)、夜間血壓下降明顯者(dippers)、夜間血壓下降不明顯者(non-dippers)、和夜間血壓上升者(risers)。再以統計方法分析各組間894G>T內皮一氣化氮合成?多型態的發生率是否有差異。結果　本研究選取之原發性高血壓患者其eNOS之894G>T多型態的發生率與過去研究報告結果相符。若將夜間血壓下降不明顯者和夜間血壓上升者合稱為夜間血壓未下降組（non-dipper group，計52人）；將夜間血壓下降極明顯者和夜間血壓下降明顯者合併起來稱為夜間血壓下降組（dipper group，計49人）；兩組比較發現：夜間血壓未下降組之eNOS 894G>T多型態的發生率較夜間血壓下降組有增加之趨勢，但未達到統計意義。然而若單獨將夜間血壓上升者（計8人）之eNOS 894G>T多型態發生率與夜間血壓下降明顯者（計45人）相比，則前者較後者明顯為高（基因型發生率差異p值為0.021；單套對偶基因型發生率差異p值為0.028）。多變項分析發現，校正年齡、性別、體質量指數、糖尿病、高血脂症和吸菸等變項後eNOS 894G>T多型態仍是預測夜間血壓上升者的獨立指標（危險比為7.95；95%信賴區間為1.36至46.4；p值為0.021）。結論　eNOS之894G>T多型態和原發性高血壓患者之晝夜血壓變化有關。此發現有臨床治療之意義，但仍需要大規模之研究加以確認。

Background: Human essential hypertension has a genetic basis, and hypertension is associated with altered endothelial nitric oxide (NO) release. We hypothesized that functional alterations of the endothelium-derived NO pathway in the presence of the 894G＞T polymorphism of the endothelial NO synthase (eNOS) gene may be related to circadian variation of blood pressure in patients with essential hypertension. Methods: A total of 101 ambulatory patients (49 men, 52 women) with essential hypertension were recruited in this study. Noninvasive ambulatory blood pressure monitoring and genotyping by polymerase chain reaction amplification of all subjects were performed. The patients were then classified into four groups according to their dipping status: extreme dippers, dippers, non-dippers, and risers. Chi-square test was used for comparison of the allelic and genotypic frequencies among different groups. Results: The frequencies of the genotypic and allelic frequencies in the study population were comparable to previous reports. There was a trend of increase of genotypic and allelic frequencies of the 894G＞T polymorphism in the non-dipper group (non-dippers + risers; n=52) as compared to the dipper group (dippers + extreme dippers; n=49), although the difference was not statistically significant. However, a significant increase in the genotypic (p=0.021) frequency and allelic frequency (p=0.028) of the 894G＞T variant in the risers (n=8), compared to those of the dippers (n=45) was noted. After adjustment for age, gender, body mass index, diabetes mellitus, hyperlipidemia, and smoking status, the presence of 894G＞T variant remained a significant predictor of risers (odds ratio 7.95; 95% C.I.=1.36-46.4; p=0.021). Conclusions: In this study, a significant association of the 894G＞T variant with circadian variation of BP in patients with essential hypertension was demonstrated. These findings are clinically relevant and warrant further investigation in a larger study.