Isolated interstitial nodal spaces may facilitate preferential solute and fluid mixing in the rat renal inner medulla

Anita T. Layton, Rebecca L. Gilbert, Thomas L. Pannabecker

Research output: Contribution to journalArticle

13 Scopus citations

Abstract

Recent anatomic findings indicate that in the upper inner medulla of the rodent kidney, tubules, and vessels are organized around clusters of collecting ducts (CDs). Within CD clusters, CDs and some of the ascending vasa recta (AVR) and ascending thin limbs (ATLs), when viewed in transverse sections, form interstitial nodal spaces, which are arrayed at structured intervals throughout the inner medulla. These spaces, or microdomains, are bordered on one side by a single CD, on the opposite side by one or more ATLs, and on the other two sides by AVR. To study the interactions among these CDs, ATLs, and AVR, we have developed a mathematical compartment model, which simulates steady-state solute exchange through the microdomain at a given inner medullary level. Fluid in all compartments contains Na +, Cl -, urea and, in the microdomain, negative fixed charges that represent macromolecules (e.g., hyaluronan) balanced by Na +. Fluid entry into AVR is assumed to be driven by hydraulic and oncotic pressures. Model results suggest that the isolated microdomains facilitate solute and fluid mixing among the CDs, ATLs, and AVR, promote water withdrawal from CDs, and consequently may play an important role in generating the inner medullary osmotic gradient.

Original languageEnglish (US)
Pages (from-to)F830-F831
JournalAmerican Journal of Physiology - Renal Physiology
Volume302
Issue number7
DOIs
StatePublished - Apr 1 2012

Keywords

  • Mathematical modeling
  • Urine concentrating mechanism
  • Vasculature

ASJC Scopus subject areas

  • Physiology
  • Urology

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