A phenomenologic evaluation of CO2-diffusion restriction in kidney tubules studied in an artificial membrane system

The chemical course in a multi-membrane system with interacting H+ and HCO3 ions has been described phenomenologically as an analogy of the neutralisation reaction between secreted H+ and filtered HCO-3 ions in the proximal tubules of the kidney. It was shown that the produced CO2 gave the highest PCO2 in the asymmetrically placed reaction centre, which favours a build-up of a high intratubular PCO2. The CO2 transport was dependent on the rate-limiting permeation of the reacting ions, and the permeation could be increased by the influence of solutions of macromolecules such as carbonic anhydrase, albumin and dextran.