Gannon Bren J, Carati C J
Microcirculation and Lymphology Laboratory, Department of Anatomy, School of Medicine, & Center for Heart, Lung & Circulation Research, Flinders University, Adelaide, South Australia.
Lymphat Res Biol. 2003;1(1):55-66. doi: 10.1089/15396850360495709.
Aquaporin-1 (AQ-1) is a transmembrane water channel protein reportedly expressed in continuous capillary endothelium and intestinal lacteals. We investigated endothelial AQ-1 expression in rat intestine and mesentery, and also in lymph nodes.
Rat intestine, mesentery, and lymph nodes were immunolabeled for AQ-1, revealing membrane expression in endothelial cells of vascular continuous capillaries and venules, and of initial and conducting lymphatics. Blood vessel profiles were identified with RECA-1 and circulating FITC-albumin. In nodes, capillaries and high endothelium venules (HEVs) showed AQ-1 labeling, as did intranodal lymphatic sinusoidal endothelium and reticular cells.
The labeling pattern of vessels with RECA-1, AQ-1, circulated FITC albumin, plus elastin autofluorescence permitted identification of arteriolar, continuous, and fenestrated capillaries and lymphatic vessels in tissue sections. Strong AQ-1 expression in continuous microvascular and initial lymphatic endothelium suggests its possible involvement in tissue fluid exchange between plasma and interstitial fluid, and perhaps between interstitial fluid and initial lymph. Endothelial AQ-1 expression was strong in lymphatic sinusoidal endothelium and intense in HEVs. This described endothelial AQ-1 expression has potential implications for tissue fluid physiology. Lymph protein is known to concentrate in lymph nodes by fluid loss, so AQ-1 may facilitate lymph to plasma water flux. Starling forces may not drive this flux, and we discuss a possible osmotic mechanism; consequently we hypothesize a suite of ion pumps/channels/exchangers/cotransporters in nodal vascular (probably HEV) endothelium, acting as a net ion pump from lymph to plasma, with water following osmotically.
水通道蛋白-1（AQ-1）是一种跨膜水通道蛋白，据报道在连续性毛细血管内皮和肠乳糜管中表达。我们研究了大鼠肠道、肠系膜以及淋巴结中内皮AQ-1的表达情况。
对大鼠的肠道、肠系膜和淋巴结进行AQ-1免疫标记，结果显示在血管连续性毛细血管和小静脉的内皮细胞以及初始淋巴管和传导淋巴管的内皮细胞中有膜表达。用RECA-1和循环的异硫氰酸荧光素标记的白蛋白来识别血管轮廓。在淋巴结中，毛细血管和高内皮小静脉（HEV）显示有AQ-1标记，结内淋巴窦内皮和网状细胞也有AQ-1标记。
用RECA-1、AQ-1、循环的异硫氰酸荧光素标记的白蛋白以及弹性蛋白自发荧光对血管进行标记，能够在组织切片中识别出小动脉、连续性和有窗孔的毛细血管以及淋巴管。连续性微血管和初始淋巴管内皮中强烈的AQ-1表达表明其可能参与血浆与组织液之间，或许还参与组织液与初始淋巴之间的组织液交换。淋巴窦内皮中内皮AQ-1表达强烈，在HEV中表达更强烈。本文所描述的内皮AQ-1表达对组织液生理学具有潜在意义。已知淋巴蛋白通过液体流失在淋巴结中浓缩，因此AQ-1可能促进淋巴向血浆的水通量。Starling力可能无法驱动这种通量，我们讨论了一种可能的渗透机制；因此我们推测在淋巴结血管（可能是HEV）内皮中有一组离子泵/通道/交换体/协同转运体，作为从淋巴到血浆的净离子泵，水随之进行渗透移动。
