Kvernmo H D, Stefanovska A, Kirkeboen K A, Kvernebo K
Institute of Medical Biology, University of Tromso, Tromso, 9037, Norway.
Microvasc Res. 1999 May;57(3):298-309. doi: 10.1006/mvre.1998.2139.
The purpose of the present study was to compare the effects of endothelium-dependent [acetylcholine (ACh)] and endothelium-independent [sodium nitroprusside (SNP)] vasodilators on the oscillatory components of the cutaneous blood perfusion signals in humans. The unstimulated basal blood perfusion and the blood perfusion during iontophoretically delivered ACh and SNP were measured using laser Doppler flowmetry (LDF). The wavelet transform was calculated before spectral analysis of the measured signals. In the frequency interval from 0.0095 to 1.6 Hz the LDF signal consists of oscillations with five different characteristic frequencies. In addition to the cardiac (1 Hz) and respiratory (0.3 Hz) rhythms, three other oscillations in the regions around 0.1, 0.04, and 0.01 Hz were detected. The oscillations with the different frequencies were observed in unstimulated blood flow and also during stimulation with ACh and SNP. Compared to the unstimulated blood flow, both ACh and SNP increased the mean amplitude of the total spectrum (P < 0. 005 for both substances). The only significant difference between the effects of ACh and SNP was observed in the amplitude of oscillations with the frequency of around 0.01 Hz. ACh increased the absolute amplitude of this frequency to a greater extent than SNP in athletes (P = 0.03), whereas only a trend was observed in controls (P = 0.2). The relative amplitude, defined as the ratio between the absolute amplitude of a particular frequency interval and the mean amplitude of the total spectrum, was also higher for ACh compared to SNP both in controls (P = 0.008) and in athletes (P = 0.004), only for oscillations with the frequency of around 0.01 Hz. We conclude that ACh selectively influences the oscillatory component of around 0.01 Hz in the cutaneous blood perfusion signal to a greater extent than SNP. This finding indicates that endothelium-mediated vasodilatation is manifested as oscillations with a repetition time of approximately 1 min. The mechanisms for the endothelial dependency of this frequency remain to be elucidated. Our data indicate that spectral analysis based on wavelet transform of the cutaneous perfusion signal can be used clinically to investigate endothelial function. The described noninvasive method might be used to evaluate endothelial function for research, for diagnostic purposes, and maybe also to assess effects of therapy in cardiovascular diseases.
本研究的目的是比较内皮依赖性血管舒张剂[乙酰胆碱（ACh）]和非内皮依赖性血管舒张剂[硝普钠（SNP）]对人体皮肤血流灌注信号振荡成分的影响。使用激光多普勒血流仪（LDF）测量未刺激时的基础血流灌注以及离子电渗法给予ACh和SNP期间的血流灌注。在对测量信号进行频谱分析之前先进行小波变换。在0.0095至1.6Hz的频率区间内，LDF信号由具有五个不同特征频率的振荡组成。除了心脏（1Hz）和呼吸（0.3Hz）节律外，还检测到了在0.1、0.04和0.01Hz附近区域的另外三种振荡。在未刺激的血流中以及ACh和SNP刺激期间均观察到了不同频率的振荡。与未刺激的血流相比，ACh和SNP均增加了总频谱的平均幅度（两种物质均P<0.005）。ACh和SNP作用之间唯一显著的差异出现在频率约为0.01Hz的振荡幅度上。在运动员中，ACh使该频率的绝对幅度增加的程度大于SNP（P=0.03），而在对照组中仅观察到一种趋势（P=0.2）。在对照组（P=0.008）和运动员（P=0.004）中，对于频率约为0.01Hz的振荡，定义为特定频率区间绝对幅度与总频谱平均幅度之比的相对幅度，ACh也高于SNP。我们得出结论，ACh比SNP在更大程度上选择性地影响皮肤血流灌注信号中约0.01Hz的振荡成分。这一发现表明内皮介导的血管舒张表现为重复时间约为1分钟的振荡。该频率的内皮依赖性机制仍有待阐明。我们的数据表明，基于皮肤灌注信号小波变换的频谱分析可用于临床研究内皮功能。所描述的非侵入性方法可用于研究、诊断目的评估内皮功能，也可能用于评估心血管疾病治疗效果。
