CIRCADIAN VARIATION IN VASCULAR TONE

在不利事件的发生中存在昼夜节律变化 已经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，发病 心肌梗塞、心源性猝死和中风。为了调查 心血管疾病昼夜节律变化的潜在机制 对12例结节受试者的前臂基底血管进行了研究 动脉内注射酚妥拉明的耐受性和反应 (α-肾上腺素能阻滞剂)和硝普钠(非特异性 血管扩张剂)在上午7：00、下午2：00和晚上9：00一种昼夜节律变化 观察到前臂基底部血管阻力，阻力最高的是 上午较低，下午和晚上较低。前臂的缩小 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 观察硝普钠。这些发现表明，昼夜节律 血管张力存在差异，以早晨和 下午和傍晚较低。这种变化是由变化决定的。 在α交感神经血管收缩活动中，并可能在原因上导致 血压越高，心血管事件的发生率越高 在早晨的几个小时内被观察。

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.