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Updated: Sep 6, 2026

Physiology Lab Demonstration: Glomerular Filtration Rate in a Rat
Published on: July 26, 2015
Conductance studies of rat renal medulla for rapid estimation of extracellular electrolyte concentration
L Dobrowolski1, J Sadowski, E Kompanowska-Jezierska
1Department of Applied Physiology, Medical Research Centre of the Polish Academy of Sciences, Warsaw.
Abstract:
A method is described for estimation of tissue extracellular electrolytes in fresh excised rat renal medulla on the basis of its electrical conductance. The inner medulla was placed between two standard flat electrodes and the conductance was measured at a frequency of 3.5 kHz. The data were corrected for the surface area and thickness of the tissue fragment. The standard conductance so determined clearly correlated with total electrolyte concentration, and Na+ and 2(Na+ + K+) concentrations in the whole tissue (r = 0.84, 0.81 and 0.77, respectively; P < 0.001). The method enables a rapid and simple estimation of medullary extracellular electrolytes, a variable that is physiologically more meaningful than whole tissue electrolyte concentration.
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