Membrane diffusion with feedback regulation of cell volume; estimation of membrane tortuosity and diffusion coefficients |
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| Authors: | T Tenforde R Macey |
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| Affiliation: | 1. Department of Nutrition Sciences and Dietetics, Faculty of Health Sciences, International Hellenic University, Sindos, Thessaloniki, Greece;2. Sports Performance Laboratory, School of Physical Education and Sports Science, National and Kapodistrian University of Athens, Athens, Greece;3. Department of Nutrition and Dietetics, School of Health Science and Education, Harokopio University of Athens, Athens, Greece;4. Laboratory of Animal Physiology, Department of Biology, Aristotle University of Thessaloniki, Thessaloniki, Greece;5. Department of Biomedical Sciences, Faculty of Health Sciences, International Hellenic University, Sindos, Thessaloniki, Greece;6. Diabetes Center, European Association for the Study of Obesity (EASO) Obesity Center, First Propedeutic Department of Internal Medicine, Medical School, Aristotle University of Thessaloniki, AHEPA Hospital, Thessaloniki, Greece;7. Laboratory of Sports Med, School of Physical Education and Sports Science, Thessaloniki, Aristotle University of Thessaloniki, Thessaloniki, Greece |
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| Abstract: | A diffusion time-lag analysis is applied to non-electrolyte transport through membranes under conditions of constant cell volume. The Fick equation is solved subject to feedback and stirred layer boundary conditions, and an expression is derived for the time integral Q of the solute flux across the inner membrane surface. As time increases, Q approaches a linear asymptote whose slope and intercept on the time axis are, respectively, (DAγΔ/hθ)/(1 + θαγ/2) and (h2θ2/6D)(1 +θαγ/4)/(1 +θαγ/2), where Δ is the solute concentration difference across the membrane, D the solute diffusion coefficient in the membrane, h the membrane thickness, A the surface area, θ the tortuosity factor, α the ratio of membrane volume to total cell volume, and γ the fraction of surface area available for solute penetration. Estimates of θ and D are obtained using measurements on glycerol permeation of beef erythrocytes under isosmolar conditions. |
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