Hudetz A G, Wood J D, Kampine J P
Department of Anesthesiology, Medical College of Wisconsin, Milwaukee 53226, USA.
J Cereb Blood Flow Metab. 2000 Feb;20(2):220-4. doi: 10.1097/00004647-200002000-00002.
The role of nitric oxide (NO) in the mechanism of hemodilution-induced cerebral hyperemia is unclear. Based on findings in hypoxemia, the authors hypothesize that NO of neuronal origin contributes to an increase in velocity of erythrocytes in the cerebral microcirculation during anemia produced by isovolemic hemodilution. The change in erythrocyte velocity in cerebrocortical capillaries was assessed by intravital fluorescence video microscopy. A closed cranial window was implanted over the frontoparietal cortex of barbiturate-anesthetized, ventilated adult rats. Erythrocytes were labeled in vitro with fluorescein isothiocyanate and infused intravenously, and their velocity in subsurface capillaries was measured by frame-to-frame image tracking. Arterial blood was withdrawn in increments of 2 mL and replaced by serum albumin; arterial blood pressure was maintained at control level with an infusion of methoxamine. Erythrocyte velocity increased progressively, reaching 215% of baseline, as arterial hematocrit was reduced from 45% to 17%. Pretreatment of a separate group of rats with 7-nitroindazole (20 mg/kg intraperitoneally), a relatively selective inhibitor of neuronal NO synthase, abolished the increase in velocity at hematocrits greater than 20%, but the maximum velocity attained at the lowest hematocrit was similar to that in the control group. The results suggest that NO from neuronal source may contribute to the increase in capillary erythrocyte flow during moderate isovolemic hemodilution.
一氧化氮（NO）在血液稀释诱导的脑充血机制中的作用尚不清楚。基于低氧血症的研究结果，作者推测，在等容血液稀释引起的贫血期间，神经元来源的NO有助于脑微循环中红细胞速度的增加。通过活体荧光视频显微镜评估大脑皮质毛细血管中红细胞速度的变化。在巴比妥麻醉、通气的成年大鼠的额顶叶皮质上方植入一个封闭的颅骨窗口。红细胞在体外用异硫氰酸荧光素标记并静脉注射，通过逐帧图像跟踪测量其在浅表毛细血管中的速度。每次抽取2 mL动脉血并用血清白蛋白替代；通过输注甲氧明将动脉血压维持在对照水平。随着动脉血细胞比容从45%降至17%，红细胞速度逐渐增加，达到基线的215%。用7-硝基吲唑（腹腔注射20 mg/kg）对另一组大鼠进行预处理，7-硝基吲唑是一种相对选择性的神经元型一氧化氮合酶抑制剂，在血细胞比容大于20%时消除了速度的增加，但在最低血细胞比容时达到的最大速度与对照组相似。结果表明，在中等程度的等容血液稀释过程中，神经元来源的NO可能有助于毛细血管红细胞流量的增加。
