CIRCADIAN VARIATION IN VASCULAR TONE

不利事件发生时昼夜节律变化的存在 已在几种心血管疾病中得到证实，包括 血压升高，动态心肌缺血， 心肌梗塞、心脏性猝死和中风。探讨 心血管疾病的昼夜节律变化机制，我们 对12例淋巴结受试者进行了前臂基底血管的测定， 动脉灌注酚妥拉明的阻力和反应 （α-肾上腺素能阻滞剂）和硝普钠（非特异性 在7：00 AM、2：00 PM和9：00 PM时，使用血管扩张剂）。一种昼夜变化， 观察到前臂基础血管阻力， 上午，下午和晚上较低。前臂缩小 酚妥拉明的血管阻力表现出类似的昼夜节律 分布;然而，血管扩张剂对 观察到硝普钠。这些发现表明，昼夜节律 血管张力存在变化，早晨张力最高， 下午和晚上较低。这种变化是由变化决定的 在交感神经血管收缩活动中， 高血压和心血管事件发生率增加 在早上观察。

The presence of circadian variation in the occurrence of unfavorable events has been demonstrated in several cardiovascular conditions, including elevations in blood pressure, ambulatory myocardial ischemia, onset of myocardial infarction, sudden cardiac death, and stroke. To investigate the mechanisms underlying the circadian variation in cardiovascular disease, we studied 12 nodal subjects with determinations of basal forearm vascular resistance and the response to intraarterial infusion of phentolamine (alpha-adrenergic blocker) and sodium nitroprusside (non-specific vasodilator) at 7:00 AM, 2:00 PM, and 9:00 PM. A circadian variation in basal forearm vascular resistance was observed, resistance being highest in the morning, and lower in the afternoon and evening. Reductions in forearm vascular resistance with phentolamine showed a similar circadian distribution; however, no such variation in the vasodilator response to sodium nitroprusside was observed. These findings indicate that circadian variation exists in vascular tone, with highest tone in the morning and lower in the afternoon and evening. This variation is determined by changes in alphasympathetic vasoconstrictor activity and may causally contribute to the higher blood pressure and increased incidence of cardiovascular events observed in the morning hours.