Analysis of vasodilated effect of nitroglycerin on microvessels us ing a high speed CCD microscope

我们研究了硝酸甘油（NTG）对大（ID>100 μ m）和小（ID<100 μ m）内膜下小动脉的直径和舒张期至收缩期脉动幅度及其节段性反应的影响。在10只开胸、麻醉的猪中，使用针探头视频显微镜视频记录跳动心脏的心内膜下小动脉（n=18）。在NTG给药（25 μ g/kg iv）前和给药后1-2分钟测定肠系膜下小动脉直径。在使用三只猪的另一个实验中，我们监测了从NTG给药前到NTG给药后3分钟的内膜下小动脉（n=5）的瞬时反应。在NTG给药后约1.5分钟，NTG使大的内膜下小动脉扩张13*4%（平均值 *SD，n=10，p<0.01），但不使小的内膜下小动脉扩张（2* 2%，n=8，不显著）。然而，小动脉对NTG的反应在早期阶段是短暂的，尤其是在较高剂量时。NTG给药后1.5min内大动脉内径从舒张期到收缩期的变化率为32.4%，明显大于对照组的19.8%（p<0.05）。此时，NTG几乎没有改变小内膜下小动脉的搏动幅度（16*8 vs. 17* 6%，NS），但在早期阶段短暂增加。总之，NTG在其脉冲（静脉内）反应的平台期（NTG后约1.5分钟）扩张了大的内膜下小动脉。NTG在1.5min时可增强大动脉内膜下小动脉的舒张期至收缩期的搏动幅度，在1.5min时可增强小动脉的舒张期至收缩期的搏动幅度，在1.5min时可增强小动脉的舒张期至收缩期的搏动幅度。

We examined the effect of nitroglycerin (NTG) on the diameter and diastolic-tosystolic pulsation amplitude of large (ID>100 mum) and small (ID<100 mum) subendocardial arterioles with their segmental responses. in 10 open-chest, anesthetized pigs, subendocardail arterioles of beating hearts (n=18) were videorecorded using a needle-probe videomicroscope. Subendocardial arteriolar diameter was determined before and 1-2 min after NTG administration (25 mug/kg iv). In an additional experiment using three pigs, we monitored the transient response of subendocardial small arterioles (n=5) from the time before NTG administration until 3 min after NTG.NTG dilated large subendocardial arterioles by 13*4% (mean*SD, n=10, p<0.01) at about 1.5 min after NTG, but not small subendocardial arterioles (2*2%, n=8, not significant). However, the small arterioles responded transiently to NTG in an earlier phase, especially to a higher dose. The percent diameter change of large subendocardial arterioles between diastole and systole at 1.5 min after NTG administration was 32 4%, which was larger than that under control conditions (19*8%, p<0.05). The pulsation amplitude of small subendocardial arterioles at this time was almost unchanged by NTG (16*8 vs. 17*6%, NS) but increased transiently in an earlier phase. In conclusion, NTG dilated large subendocardial arterioles on the plateau phase of its impulse (intravenously) response (-1.5 min after NTG). It dilated small arterioles transiently at -15 s, but not at 1.5 min. NTG enhanced the diastolic-to-systolic pulsation amplitude of large subendocardial arterioles at 1.5 min and transiently of small arterioles.