Urea transport in a distributed loop model of the urine-concentrating mechanism.


Journal Article

Continuously distributed loops of Henle were used in a central core model of the rat kidney's urine-concentrating mechanism to investigate the importance of overlapping loops for three different modes of urea transport in the long loops of Henle: 1) urea-impermeable loops, 2) urea-permeable loops (as indicated by perfused tubule experiments), and 3) loops with urea-permeable descending limbs and active urea transport out of thin ascending limbs. Mode 1 produces high papillary tip osmolality in accordance with tissue slice experiments, but the relative contribution of urea to the osmolality of the central core and the long descending limbs is below experimental measurements. Mode 2 generates no significant osmolality increase in the inner medulla, in agreement with other model studies. Mode 3 produces high papillary tip osmolality with a substantial contribution of urea to the osmolality of the core and the descending limbs, which is more in accordance with experiments. The results suggest that 1) overlapping loops may produce a cascade effect that contributes to the inner medullary concentrating mechanism and that 2) new experiments are needed to more certainly ascertain the urea transport characteristics of the thin ascending limbs.

Full Text

Duke Authors

Cited Authors

  • Layton, HE

Published Date

  • April 1990

Published In

Volume / Issue

  • 258 / 4 Pt 2

Start / End Page

  • F1110 - F1124

PubMed ID

  • 2330976

Pubmed Central ID

  • 2330976

Electronic International Standard Serial Number (EISSN)

  • 2163-5773

International Standard Serial Number (ISSN)

  • 0002-9513

Digital Object Identifier (DOI)

  • 10.1152/ajprenal.1990.258.4.f1110


  • eng