J Korean Soc Pediatr Nephrol.  2005 Apr;9(1):1-7.

Urine Concentrating Mechanism and Urea Transporters

• Kim DU

Abstract

The production of concentrated urine is achieved by countercurrent multiplication in the renal medulla. The single effect of the outer medulla is the active NaCl reabsorption in the thick ascending limb, while the single effect of the inner medulla is the passive efflux of NaCl through the thin ascending limb. The passive mechanism in the inner medulla requires a high interstitial urea concentration which is maintained by intrarenal recycling of urea. During the past decade, many transport proteins involved in the urine concentrating mechanism have been cloned, which has enabled us to understand the countercurrent multiplication mechanism on a molecular basis. This review will summarize the locations and functions of the renal medullary transport proteins, and the recent insights that have been acquired into the long term regulation of urea transporters.

Keyword

Countercurrent multiplication; Water; NaCl; Urea

MeSH Terms

Carrier Proteins
Clone Cells
Extremities
Recycling
Urea*
Water
Carrier Proteins
Urea
Water