Role of villus microcirculation in intestinal absorption of glucose: coupling of epithelial with endothelial transport
Role of villus microcirculation in intestinal absorption of glucose: coupling of epithelial with endothelial transport
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DOI：
10.1113/jphysiol.2003.043257
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发表时间：
2003-12-01
影响因子：
5.5
通讯作者：
Michel, CC
中科院分区：
文献类型：
--
作者：
Pappenheimer, JR;Michel, CC
空肠绒毛中的毛细血管吸收营养的速率（每克组织）比其他组织（包括收缩骨骼肌和大脑）中的毛细血管高几百倍。我们在这里提出了一个综合假设来解释这些异常大的跨内皮通量及其与上皮转运的关系。方程估计葡萄糖浓度梯度跨绒毛毛细血管壁，沿着细胞旁通道和跨吸收细胞的虚拟连接侧膜。高浓度的葡萄糖通过细胞间通道中的对流-扩散穿过侧膜排放到细胞间虚拟空间，并被递送到绒毛毛细血管的近腔表面，而没有显著的浓度损失。因此，连接后的细胞旁转运提供了上皮和内皮转运之间的串联，并使得吸收到血液中所需的大的跨内皮浓度梯度成为可能。我们的分析表明，增加绒毛，毛细血管血流量和渗透性表面积积（PS）的吸收机制的重要组成部分：上皮运输正常的消化负荷不能持续没有伴随增加毛细血管血流量和PS。在麻醉动物中发现的低肠吸收率可能归因于对上皮转运的正常绒毛微血管反应的抑制。
Capillaries in jejunal villi can absorb nutrients at rates several hundred times greater (per gram tissue) than capillaries in other tissues, including contracting skeletal muscle and brain. We here present an integrative hypothesis to account for these exceptionally large trans-endothelial fluxes and their relation to epithelial transport. Equations are developed for estimating concentration gradients of glucose across villus capillary walls, along paracellular channels and across subjunctional lateral membranes of absorptive cells. High concentrations of glucose discharged across lateral membranes to subjunctional intercellular spaces are delivered to abluminal surfaces of villus capillaries by convection-diffusion in intercellular channels without significant loss of concentration. Post-junctional paracellular transport thus provides the series link between epithelial and endothelial transport and makes possible the large trans-endothelial concentration gradients required for absorption to blood. Our analysis demonstrates that increases of villus; capillary blood flow and permeability-surface area product (PS) are essential components of absorptive mechanisms: epithelial transport of normal digestive loads could not be sustained without concomitant increases in capillary blood flow and PS. The low rates of intestinal absorption found in anaesthetised animals may be attributed to inhibition of normal villus microvascular responses to epithelial transport.