Gillin A G, Sands J M
Department of Renal Medicine, Royal Prince Alfred Hospital, Sydney, Australia.
Semin Nephrol. 1993 Mar;13(2):146-54.
Urea transport within the kidney is regulated and varies dramatically between different nephron segments. The terminal IMCD displays very high rates of transepithelial urea transport enabling delivery of large amounts of urea into the deepest portions of the inner medulla to maintain a high interstitial osmolality for concentrating the urine maximally. Urea in the terminal IMCD is transported by a specific urea transporter that is stimulated by vasopressin and hyperosmolarity. Although the urea transporter has not been cloned, individuals have been identified who lack the urea transporter. Individuals who lacked the Kidd antigen (a minor blood group antigen) also lacked carrier-mediated urea transport in their erythrocytes (and presumably in their kidneys). These same subjects were unable to concentrate their urine above 800 mOsm following overnight water deprivation. This experiment of nature illustrates the critical importance of the urea transporter to concentrating ability in humans.
肾脏内的尿素转运受到调节，并且在不同的肾单位节段之间存在显著差异。终末内髓集合管显示出非常高的跨上皮尿素转运速率，能够将大量尿素输送到内髓最深部，以维持高间质渗透压，从而最大限度地浓缩尿液。终末内髓集合管中的尿素通过一种特定的尿素转运体进行转运，该转运体受血管加压素和高渗刺激。尽管该尿素转运体尚未被克隆，但已鉴定出缺乏该尿素转运体的个体。缺乏基德抗原（一种次要血型抗原）的个体，其红细胞（可能还有肾脏）中也缺乏载体介导的尿素转运。这些受试者在禁水过夜后，无法将尿液浓缩至800 mOsm以上。这一自然实验说明了尿素转运体对人类浓缩能力的至关重要性。
