Concentrating models of the renal inner medulla can be classified according to external free-energy balance into passive models (positive values) and models that require an external energy source (negative values). Here we introduce an online computational tool that implements the equations of Stephenson and colleagues to calculate external free-energy balance at steady state for the inner medulla (http://helixweb.nih.gov/ESBL/FreeEnergy/ temporary login: clp temporary password: Esbl!@#$ login to be removed upon acceptance of this paper). Here 'external free-energy balance' means the sum of free-energy flows in all streams entering and leaving the inner medulla. The program first assures steady-state mass balance for all components and then tallies net external free-energy balance for the selected flow conditions. Its use is illustrated by calculating external free-energy balance for an example of the passive concentrating model taken from the original paper by Kokko and Rector.
- inner medulla
- free energy
- mathematical model
- urine concentrating mechanism
- Copyright © 2012, American Journal of Physiology - Renal Physiology