Clark H B, Hartman B K, Raichle M E, Preskorn S H, Larson K B
J Cereb Blood Flow Metab. 1982;2(2):187-96. doi: 10.1038/jcbfm.1982.18.
An intravenous injection method to measure cerebral vascular extraction fractions of highly diffusible substances in the rat is described. The brain extraction fractions of 3H-labeled water (Ew) and ethanol (Ee) were defined as the ratio of either of those tracers to the freely diffusible reference tracer, 14C-butanol, in the brain, divided by the ratio of the tracers available for the extraction during the time between simultaneous intravenous injection of the tracers and decapitation of the rat. Ew and Ee were measured in five regions of brain, including brainstem and cerebellum, under PaCO2 conditions ranging from 15 to 85 mm Hg. The extraction fractions for both test tracers were shown to vary with PaCO2-induced flow changes according to the equation, ln(1 - E) = -PS/F. When PS/F values calculated from regional measurements of Ew and Ee were plotted versus PaCO2, least squares regression equations of the plots could be used to compare permeabilities of both tracers at any given PaCO2 value. Ratios of the permeabilities of water and ethanol varied regionally but were relatively constant in a given region under different flow states. This intravenous injection method allows for accurate measurement of the extraction fractions of even highly diffusible tracers under varied flow conditions in all brain regions regardless of arterial blood supply.
本文描述了一种用于测量大鼠脑血管对高扩散性物质提取分数的静脉注射方法。3H标记水（Ew）和乙醇（Ee）在脑中的提取分数定义为脑中这些示踪剂与自由扩散参考示踪剂14C-丁醇之一的比率，除以在同时静脉注射示踪剂至大鼠断头期间可用于提取的示踪剂的比率。在15至85 mmHg的PaCO2条件下，在包括脑干和小脑在内的五个脑区测量了Ew和Ee。两种测试示踪剂的提取分数均显示根据公式ln(1 - E) = -PS/F随PaCO2诱导的血流变化而变化。当根据Ew和Ee的区域测量计算出的PS/F值与PaCO2作图时，该图的最小二乘回归方程可用于比较任何给定PaCO2值下两种示踪剂的通透性。水和乙醇通透性的比率在不同区域有所不同，但在给定区域内不同血流状态下相对恒定。这种静脉注射方法允许在所有脑区的不同血流条件下准确测量甚至是高扩散性示踪剂的提取分数，而不受动脉血供的影响。
