Interaction between sodium ion and non-electrolytes in the countercurrent systems of the kidney
| Autor: | John D. Abernethy |
|---|---|
| Rok vydání: | 1973 |
| Předmět: |
Statistics and Probability
Cell Membrane Permeability Nitrogen Countercurrent exchange Diffusion Sodium Tubular fluid Countercurrent multiplication Thermodynamics chemistry.chemical_element Electrolyte Urine Kidney Helium Models Biological General Biochemistry Genetics and Molecular Biology Ion Loop of Henle medicine Animals Argon Countercurrent Distribution Kidney Medulla General Immunology and Microbiology Applied Mathematics General Medicine medicine.anatomical_structure chemistry Modeling and Simulation General Agricultural and Biological Sciences Mathematics |
| Zdroj: | Journal of Theoretical Biology. 39:589-600 |
| ISSN: | 0022-5193 |
| DOI: | 10.1016/0022-5193(73)90070-2 |
| Popis: | A change in the electrolyte concentration in a multicomponent system will in general change the activity of non-electrolyte species, a particular example being the salting-out of dissolved gases (although for some solutes a salting-in effect occurs). It follows that countercurrent multiplication of sodium ions in the renal medulla will inevitably be associated with change in activity of non-electrolytes since this process is characterized by two orthogonal [Na + ] gradients in the multiplier loop, the one longitudinal, the other transverse. Using a single loop model we show that the two [Na+] gradients act independently to produce opposing effects on activity so that given, say, a salting-out effect, the longitudinal gradient effects an increase in activity and the transverse a decrease, both being dependent on the magnitude of the interaction. In the latter case, since attenuation results from direct involvement of the solute in the countercurrent multiplication process, the diffusion coefficient of necessity also has a positive influence. In the non-steady state we show that a measure of the time taken to reach equilibrium varies with the square of the transit time of tubular fluid. This means that there are likely to be transient activity differences between the two countercurrent systems, active and passive, in the medulla. Urine appears to be in equilibrium with the inner medulla and so will reflect these activity changes in the steady and non-steady state. This analysis is consistent with previous experimental findings on urinary inert gases. These results could suggest an indirect method of monitoring countercurrent multiplication of sodium. There are also implications for clinical studies since it is often assumed that urine reflects blood concentrations of biologically inert solutes. |
| Databáze: | OpenAIRE |
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