Pannabecker Thomas L, Dantzler William H
University of Arizona Health Sciences Center, Department of Physiology, AHSC 4130, 1501 N. Campbell Ave., Tucson, AZ 85724-5051, USA.
Am J Physiol Renal Physiol. 2007 Sep;293(3):F696-704. doi: 10.1152/ajprenal.00231.2007. Epub 2007 Jul 3.
Three-dimensional architecture of vasculature and nephrons in rat renal papilla was assessed by digital reconstruction. Descending vasa recta (DVR), ascending vasa recta (AVR), descending thin limbs (DTLs), ascending thin limbs (ATLs), and collecting ducts (CDs) were identified with antibodies against segment-specific proteins. DTLs are distributed nonuniformly in transverse sections of papilla, but lateral compartmentation between DTLs and CD clusters that occurs in outer IM makes no contribution to concentrating mechanism in papilla. ATLs are distributed nearly uniformly throughout IM. Vasa recta within approximately 2 mm of the papilla tip are primarily fenestrated vessels; therefore, AVR and DVR can only be determined by blood flow direction. CDs within approximately 500 microm of the papilla tip have nearly 100% greater circumference than CDs within first 1-2 mm below the IM base. Return of water to general circulation from deep papillary CDs appears to be facilitated by a 150% increase in the number of AVR closely abutting these CDs. Consequently, average fractional CD surface area abutting AVR is 0.61, about the same as that (0.54) for smaller CDs that lie near the IM base. Interstitial nodal compartments, bounded by CDs, ATLs, and AVR, surround CDs along the axis of the IM. Fewer ATLs exist in the final 1 mm, as there are fewer loops and the number of these nodal arrangements is therefore reduced. However, tips of many of those loops reaching this area have bends with 50-100% greater transverse lengths than bends of loops near the IM base. This may be significant for solute movement out of loop bends.
通过数字重建评估大鼠肾乳头中血管和肾单位的三维结构。用针对节段特异性蛋白的抗体识别直小血管降支（DVR）、直小血管升支（AVR）、细段降支（DTL）、细段升支（ATL）和集合管（CD）。DTL在乳头横切面上分布不均匀，但在外髓质中DTL与集合管簇之间的侧向分隔对乳头的浓缩机制没有贡献。ATL几乎均匀地分布于整个髓质。靠近乳头尖端约2mm内的直小血管主要是有孔血管；因此，AVR和DVR只能通过血流方向来确定。靠近乳头尖端约500微米内的集合管的周长比髓质基部以下最初1 - 2mm内的集合管大近100%。紧密邻接这些集合管的AVR数量增加150%，似乎促进了深部乳头集合管中的水回流到体循环。因此，邻接AVR的集合管平均表面积分数为0.61，与靠近髓质基部的较小集合管的表面积分数（0.54）大致相同。由集合管、ATL和AVR界定的间质节点隔室沿髓质轴围绕集合管。在最后1mm内存在的ATL较少，因为袢较少，因此这些节点排列的数量减少。然而，许多到达该区域的袢的尖端具有比靠近髓质基部的袢的弯曲更大50 - 100%的横向长度。这可能对溶质从袢弯曲处移出具有重要意义。
