UREA TRANSPORT AND THE URINARY CONCENTRATING MECHANISM

对分离的肾上皮细胞的研究和数学模型研究包括 正在开展尿素在选矿中的作用研究 机制，并界定内部集中的机制 延髓。内髓集合管是异质的。 关于熊毛虫的渗透性。从外三分之一收集风管 的内髓对尿素的渗透性很低，就像来自 髓射线和外髓。相比之下，从 内髓集合管的内三分之二有一个极 对尿素的高渗透性，40×10-5厘米/S。这种集合管模式 尿素通透性使内髓内轴向尿素梯度最大化 通过延缓尿素的吸收到乳头状尖端附近有效的 血流量最低。乳头状表面上皮细胞被发现有一个 对尿素渗透性低(1×10-5厘米/S)，表面积相对较小 至内髓集合管。由此得出结论：尿素的转运 穿过乳头状上皮不太可能对 尿素向髓内间质输送。

Studies of isolated renal epithelia and mathematical modelling studies are being carried out to investigate the role of urea in the concentrating mechanism and to define the mechanism of concentration in the inner medulla. The inner medullary collecting duct was found to be heterogenous with respect to urfea permeability. Collecting ducts from the outer third of the inner medulla have a low permeability to urea like those from the medullary rays and outer medulla. In contrast, collecting ducts from the inner two-thirds of the inner medullary collecting duct have an extremely high permeability to urea, 40 x 10-5 cm/s. This pattern of collecting duct urea permeabilities maximizes the axial urea gradient in the inner medulla by delaying urea absorption to near the papillary tip where the effective blood flow is lowest. The papillary surface epithelium was found to have a low permeability to urea (1 x 10-5 cm/s) and a small surface area relative to inner medullary collecting ducts. It is concluded that urea transport across the papillary epithelium is unlikely to contribute significantly to urea delivery to the inner medullary interstitium.