小鼠长髓襻肾单位在髓质的分布

目的 肾髓质渗透梯度的形成与髓襻走行及转运功能关系密切，本研究拟建立长髓袢肾单位在髓质的走行规律。方法C57BL6/J小鼠3只，灌流固定后取肾组织块，树脂812包埋，垂直肾长轴连续半薄切片，从肾被膜到内髓，共得到2 000张2.5μm厚的连续切片，显微镜下获取数字图像，计算机配准，C语言编程，进而追踪26条长髓襻肾单位。结果 长髓襻肾单位来自中层和近髓质区的皮质，其髓襻襻曲分布在内髓不同水平，最深的可达肾乳头。通过数字追踪发现，在外髓内带外侧区，髓襻降支细段起始部高度盘曲走行，其盘曲部分的长度是其直线距离的2倍。在盘曲走行中，与同源的髓襻升支粗段间隔排列。最长的长髓襻升支粗段走行在外髓内带的血管丛。在外髓内带的内侧区，髓襻降支细段与髓襻升支粗段紧密相邻，直行进入内髓。结论 降支细段在外髓内带高度盘曲走行，在增加了这一节段长度的同时，也增加了这一节段的转运功能，提示此结构特征对该区域的渗透梯度形成可能产生重要影响。

Distribution of the mouse long loop nephron in medulla

Objective The formation of the osmotic gradient in the renal medulla has close relation with epithelial transport and the spatial arrangement of Henle,s loops and vessels.The objective of the present study was to investigate the tubular course of the long loop nephrons (LLN) in the medulla. Methods Three C57BL/6J mice were fixed by perfusion and embedded in Epon 812.Tissue blocks were cut perpendicularly to the longitudinal axis of the kidney,and a total of 2 000serial sections with a thickness of 2.5 μm were obtained from the surface of the kidney to the inner medulla.Using image recording and alignment, 26 LLN were identified,traced and 3D-reconstructed with a series of computer programs written in the C programming language. Results The LLN initiated at the mid-cortex and juxtamedullary cortex of the kidney.Their bends were located at various levels of theinner medulla,but the deepest bends reached the papillary.Interestingly,descending thin limbs of the LLN ran tortuously in the outer part of the inner stripe of the outer medulla,and the length of the tortuous part of the tubules was two times of the direct distance in that area.The winding descending thin limb ran in distance but paralleled with its isogenous thick ascending limb.The thick ascending limbs of the longer LLN ran in the vascular bundles in the inner stripe of the outer medulla.In the inner part of the inner stripe of the outer medulla,descending thin limbs ran adjacently with thick ascending limbs. Conclusion A winding course of descending thin limbs in the inner stripe of the outer medulla of LLN increases in the length of the corresponding segments,suggesting an impact in the formation of the osmotic gradie