盐敏感者盐负荷期间交感神经活性研究

The study of sympathetic nervous activity during the period of chronic salt loading in saltsensitive subjects

为探讨盐敏感性个体交感神经活性与盐负荷的关系，对２３例２３～４０岁的血压正常者采用慢性盐负荷的方法确定盐敏感者（ＳＳ），观察盐负荷期间以及冷加压试验中血浆去甲肾上腺素（ＰＮＥ）和血浆肾上腺素（ＰＥ）水平、心率变异性、动态血压、２４小时尿Ｎａ＋排泄量和红细胞Ｎａ＋含量等变化。发现与盐不敏感者（ＮＳＳ）相比，ＳＳ者于盐负荷及应激状态下伴随血压的升高，ＰＮＥ和ＰＥ均增高，尤以ＰＮＥ为著；心率变异性频域分析中夜间低频（ＬＦ）和ＬＦ与高频（ＨＦ）成份比值（ＬＦ／ＨＦ）增加；动态血压中的夜间血压偏高，昼夜血压差值缩小。盐负荷期间２４小时尿Ｎａ＋排泄量降低，红细胞Ｎａ＋含量显著升高，且前者与ＰＮＥ呈负相关（ｒ＝－０．５４，Ｐ＜０．０５）。上述结果表明，本研究年龄段的血压正常盐敏感者存在高盐介导的交感神经活性增高表现。

The purpose of this study was to investigate the changes of sympathetic nervous activity during the period of chronic salt loading in saltsensitive normotensive subjects. Chronic dietary salt loading tests were undertaken to determine salt sensitivity (SS) in 23 normotensive subjects. Plasma norepinephrine (PNE) and epinephrine (PE) concentration, heart rate variability analysis, ambulatory blood pressure, urinary sodium and potassium and erythrocyte sodium content were determined before and during the period of salt loading respectively. PNE and PE were also measured in the course of the cold pressor test. Compared with nonsaltsensitive subjects (NSS), the levels of PNE and PE increased during the high salt intake stage and the cold pressor test (P<005 or 0.01). Low frequency (LF) and the ratio of LF to high frequency (LF/HF) of heart rate variability during the nighttime were also higher in SS than in NSS (P<005 or 0.01). The average level of nocturnal blood pressure was much higher and the change of blood pressure from day to night was smaller in SS (P<005 or 0.01). It was also found that the level of renal sodium excretion decreased and the erythrocyte sodium content increased during the high salt intake stage (P<005 or 0.01), and 24 hour urinary sodium excretion was negatively correlated with the level of PNE (r=-0.54, P<005). These findings suggested that the level of sympathetic nervous activity in saltsensitive normotensive subjects increased during the period of salt loading.