Analysis of vasodilated effect of nitroglycerin on microvessels

我们研究了硝酸甘油（NTG）对大（ID>100mum）和小（ID<100mum）心内膜下小动脉直径和舒张-收缩脉动幅值及其节段性反应的影响。在10头开胸麻醉的猪中，使用针探针视频显微镜记录了心脏跳动的心内膜下小动脉（n=18）。心内膜下小动脉直径测定于给药前和给药后1-2分钟（25mum/kg iv）。在另一项实验中，我们用三只猪监测心内膜下小动脉（n=5）从给药前到给药后3分钟的短暂反应。NTG使心内膜下大小动脉扩张13(]SY.+-。[) %（平均）% (+-)%[)SD,n=10, p<0.01)在NTG后约1.5 min，但不包括心内膜下小动脉(2)。[)2%, n=8，不显著)。然而，小动脉在早期阶段对NTG有短暂的反应，特别是对高剂量。给药后1.5 min心内膜下大动脉舒张期与收缩期直径变化百分率为32（±±）。[)4%，大于对照条件下(19(]SY.+-。(8%, p < 0.05)。此时心内膜下小动脉的搏动幅度几乎未受NTG (16（]SY.+-）的影响。[)8 .17] [a] [a][)6%， NS)，但在早期阶段短暂增加。综上所述，NTG在其脉冲（静脉）反应的平台期（NTG后-1.5分钟）扩张了心内膜下大动脉。它在-15 s时短暂扩张小动脉，但在1.5 min时没有。NTG增强了心内膜下大动脉舒张-收缩脉动幅值；在1.5分钟和小动脉短暂的Es。

We examined the effect of nitroglycerin (NTG) on the diameter and diastolic-to-systolic pulsation amplitude of large (ID>100mum) and small (ID<100mum) 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 (25mum/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(]SY.+-。[)4% (mean(]SY.+-。[)SD,n=10, p<0.01) at about 1.5 min after NTG,but not small subendocardial arterioles (2(]SY.+-。[)2%, n=8, not significant). However, the small arterioles responded transiently to NTG in an earlier phase, especially to higher dose. The percent diameter change of large subendocardial arterioles between diastole and systole at 1.5 min after NTG administration was 32(]SY.+-。[)4%, which was larger than that under control conditions (19(]SY.+-。[)8%, p<0.05). The pulsation amplitude of small subendocardial arterioles at this time was almost unchanged by NTG (16(]SY.+-。[)8 vs.17(]SY.+-。[)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 subendocdardial arteop ; es at 1.5 min and transiently of small arterioles.