Bereczki D, Wei L, Otsuka T, Hans F J, Acuff V, Patlak C, Fenstermacher J
Department of Neurological Surgery, State University of New York, Stony Brook 11794-8122.
Am J Physiol. 1993 May;264(5 Pt 2):H1360-9. doi: 10.1152/ajpheart.1993.264.5.H1360.
The increase in local cerebral blood flow (LCBF) caused by hypercapnia may be mainly accomplished by raising the velocity of plasma and/or red blood cell (RBC) flow through the microvessels and not by perfusing more capillaries. This suggestion was tested in awake rats exposed to 8% CO2 and in control rats. LCBF was measured by the 14C-labeled iodoantipyrine method. The volume of blood in small parenchymal microvessels was estimated from the distribution spaces of 125I-labeled serum albumin (RISA) and 55Fe-labeled RBCs. Hypercapnia elevated LCBF 2.0- to 3.5-fold in the 40 brain areas studied, marginally raised the RBC spaces, and significantly increased the RISA and whole blood distribution spaces (approximately 25 and 19%, respectively). These changes in microvessel distribution volumes could be the result of perfusing a slightly larger fraction of capillaries (recruitment), increasing microvessel diameter somewhat, or both. With hypercapnia, the mean transit times fell to approximately 45% of control, which indicated that LCBF was mainly increased by raising the velocity of RBC and plasma flow through already perfused microvessels. Overall, few, if any, capillaries or other microvessels were recruited by hypercapnia.
高碳酸血症引起的局部脑血流量（LCBF）增加可能主要是通过提高血浆和/或红细胞（RBC）流经微血管的速度来实现的，而不是通过灌注更多的毛细血管来实现。这一观点在暴露于8%二氧化碳的清醒大鼠和对照大鼠中进行了验证。采用14C标记的碘安替比林法测量LCBF。根据125I标记的血清白蛋白（RISA）和55Fe标记的红细胞的分布空间估算实质内小微血管中的血容量。在研究的40个脑区中，高碳酸血症使LCBF升高了2.0至3.5倍，使红细胞空间略有增加，并显著增加了RISA和全血分布空间（分别约为25%和19%）。微血管分布容积的这些变化可能是由于灌注了稍大比例的毛细血管（募集）、微血管直径略有增加或两者共同作用的结果。在高碳酸血症时，平均通过时间降至对照值的约45%，这表明LCBF主要是通过提高红细胞和血浆流经已灌注微血管的速度而增加的。总体而言，高碳酸血症几乎没有募集到毛细血管或其他微血管（如果有的话）。
