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

我们观察了硝酸甘油(NTG)对心内膜下大动脉(ID&gt；100um)和小动脉(ID&lt；100um)直径和舒张期-搏动幅度的影响及其节段性反应。在10只开胸麻醉猪上，用针刺探头电视显微镜记录了18只心脏不停跳心内膜下小动脉。静脉注射NTG(25ug/kg)前、后1~2min测定心内膜下小动脉内径。在另外一个实验中，我们监测了从给药前到给药后3分钟心内膜下小动脉(n=5)的瞬时反应。NTG在给药后1.5分钟时心内膜下大小动脉扩张了13×4%(平均值*SD，n=10，p&lt；0.01)，但心内膜下小动脉扩张不明显(2*2%，n=8，无显著意义)。然而，在较早的阶段，小动脉对NTG有短暂的反应，尤其是对较高剂量的反应。静脉注射NTG后1.5min，心内膜下大动脉舒缩期直径变化率为32.4%，高于对照组的19.8%(P<0.05)。心内膜下小动脉的搏动幅度在NTG作用下几乎没有变化(16×8比17×6%，NS)，但在早期有一过性增加。总之，NTG在其脉冲(静脉)反应的平台期(NTG后-1.5分钟)扩张大的心内膜下小动脉。在-15 S时，小动脉一过性扩张，但在1.5min时未见扩张。NTG使心内膜下大动脉1.5min舒缩搏动幅度增加，对小动脉一过性增加。

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.