Chang H Y, Chen C W, Hsiue T R, Chen C R
Department of Internal Medicine, College of Medicine, National Cheng Kung University, Tainan, Taiwan, Republic of China.
Am J Physiol. 1997 Jan;272(1 Pt 2):H272-8. doi: 10.1152/ajpheart.1997.272.1.H272.
The effects of glibenclamide (GLB), a specific blocker of ATP-sensitive potassium (KATP) channels, and tetraethylammonium (TEA) on modulating the regulation of diaphragmatic microcirculation were assessed in anesthetized mechanically ventilated rats. With bicarbonate-buffered Ringer solution continuously suffusing the left hemidiaphragm, microcirculatory blood flow was recorded by laser-Doppler flowmetry (QLDF). Hemorrhagic hypotension (HH) was induced via bleeding into a pressure reservoir. Five sets of experiments were performed. In set 1 (n = 6), the vasodilator effect of diazoxide (3 x 10(-4) M) was abolished after a 30-min suffusion with GLB, whereas the vasodilator effect of sodium nitroprusside (3 x 10(-6) M) remained the same. In set 2 (vehicle + HH; n = 23), a stepwise reduction in systemic arterial blood pressure (ABP) induced two distinct patterns of microvascular responses. Regulation of QLDF could be observed in pattern A animals in a range of ABP from 113 to 52 mmHg, whereas QLDF in pattern B animals rose progressively with declining ABP. In set 3 (GLB + HH; n = 17), baseline values of QLDF were not significantly affected after a 30-min suffusion of GLB (10(-5) M). During HH, two microvascular patterns similar to those in set 2 were observed. GLB significantly potentiated the reduction in QLDF in pattern A animals. In contrast, GLB had no effect on QLDF in pattern B animals. In set 4 (TEA + HH; n = 17), similar microvascular responses, compared with the vehicle group, were observed during HH after a 30-min suffusion of TEA (2 x 10(-3) M). In set 5 (n = 5), baseline values of QLDF were not significantly altered during sham hypotension. We conclude that 1) KATP channels are functional but not active in the resting diaphragmatic microcirculation and 2) KATP channels can modulate regulation of the microcirculation in the resting diaphragm during HH.
在麻醉状态下进行机械通气的大鼠中，评估了格列本脲（GLB，一种ATP敏感性钾通道（KATP）的特异性阻滞剂）和四乙铵（TEA）对调节膈肌微循环的影响。用碳酸氢盐缓冲的林格氏液持续灌注左半膈肌，通过激光多普勒血流仪（QLDF）记录微循环血流量。通过向压力贮器内放血诱导出血性低血压（HH）。进行了五组实验。在第1组（n = 6）中，用GLB灌注30分钟后，二氮嗪（3×10⁻⁴ M）的血管舒张作用被消除，而硝普钠（3×10⁻⁶ M）的血管舒张作用保持不变。在第2组（溶剂 + HH；n = 23）中，系统性动脉血压（ABP）的逐步降低引发了两种不同的微血管反应模式。在模式A的动物中，ABP在113至52 mmHg范围内时可观察到QLDF的调节，而模式B的动物中，QLDF随着ABP的下降而逐渐升高。在第3组（GLB + HH；n = 17）中，用GLB（10⁻⁵ M）灌注30分钟后，QLDF的基线值未受到显著影响。在HH期间，观察到了与第2组相似的两种微血管模式。GLB显著增强了模式A动物中QLDF的降低。相比之下，GLB对模式B动物的QLDF没有影响。在第4组（TEA + HH；n = 17）中，用TEA（2×10⁻³ M）灌注30分钟后，在HH期间观察到了与溶剂组相比相似的微血管反应。在第5组（n = 5）中，在假低血压期间QLDF的基线值未发生显著改变。我们得出结论：1）KATP通道在静息膈肌微循环中具有功能但不活跃；2）KATP通道可在HH期间调节静息膈肌的微循环。
