Capillary recruitment in a theoretical model for blood flow regulation in heterogeneous microvessel networks.
Capillary recruitment in a theoretical model for blood flow regulation in heterogeneous microvessel networks.
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DOI：
10.1002/phy2.50
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发表时间：
2013-08
影响因子：
2.5
通讯作者：
Secomb, Timothy W
中科院分区：
文献类型：
--
作者：
Fry, Brendan C;Roy, Tuhin K;Secomb, Timothy W
在横纹肌中，含有运动红细胞的毛细血管数量随着代谢需求的增加而增加。这种现象被称为毛细血管募集，早已被认识到，但其机制尚不清楚。本研究采用了异质网络中代谢性血流调节的理论模型来检验毛细血管募集是动脉直径主动控制和微血管分叉处红细胞压积不均匀分配的结果。网络结构来源于发表的仓鼠肌在控制和扩张状态下的观察。动脉直径调节的模型包括血管平滑肌的长度-张力特征以及平滑肌张力对肌源性、剪切依赖性和代谢刺激的反应。血流模拟包括不均匀的红细胞压积分布。模拟了网络中对流和扩散氧输运。氧依赖性代谢信号被认为是从远端血管上游传导到小动脉。随着需氧量的增加，小动脉扩张，血流量增加，流动的小动脉和毛细血管的数量（红细胞通量高于小阈值）增加。在分叉处不平等的红细胞压积分配有助于招募和增强组织氧合。研究结果表明，在仓鼠乳状动脉制剂中观察到的毛细血管募集可能是局部控制小动脉张力和由此导致的红细胞通量不均匀变化的结果，并为观察到个体毛细血管在末端小动脉直径调节下的连续募集提供了解释。
In striated muscle, the number of capillaries containing moving red blood cells increases with increasing metabolic demand. This phenomenon, termed capillary recruitment, has long been recognized, but its mechanism has been unclear. Here, a theoretical model for metabolic blood flow regulation in a heterogeneous network is used to test the hypothesis that capillary recruitment occurs as a result of active control of arteriolar diameters, combined with unequal partition of hematocrit at diverging microvascular bifurcations. The network structure is derived from published observations of hamster cremaster muscle in control and dilated states. The model for modulation of arteriolar diameters includes length-tension characteristics of vascular smooth muscle and responses of smooth muscle tone to myogenic, shear-dependent, and metabolic stimuli. Blood flow is simulated including nonuniform hematocrit distribution. Convective and diffusive oxygen transport in the network is simulated. Oxygen-dependent metabolic signals are assumed to be conducted upstream from distal vessels to arterioles. With increasing oxygen demand, arterioles dilate, blood flow increases, and the numbers of flowing arterioles and capillaries, as defined by red blood cell flux above a small threshold value, increase. Unequal hematocrit partition at diverging bifurcations contributes to recruitment and enhances tissue oxygenation. The results imply that capillary recruitment, as observed in the hamster cremaster preparations, can occur as a consequence of local control of arteriolar tone and the resulting nonuniform changes in red blood cell fluxes, and provide an explanation for observations of sequential recruitment of individual capillaries in response to modulation of terminal arteriolar diameter.