Each day, the human kidneys filter about 140 l of primary urine from plasma. Although this ultrafiltrate is virtually free of plasma protein, the glomerular filter never clogs under physiological conditions. Upto today it is still not entirely resolved as to how the kidney accomplishes this extraordinary task. Most of the proposed models for glomerular filtration have not considered electrical effects.
In micropuncture studies, we have directly measured an electrical field across the glomerular filtration barrier. This potential difference is most likely generated by forced passage of the ionic solution of the plasma across the charged glomerular filter (‘electrokinetic potential’). As all plasma proteins are negatively charged, the electrical field across the glomerular filtration barrier is predicted to drive plasma proteins from the filter toward the capillary lumen by electrophoresis.
In this review, we examine our novel model for glomerular filtration in more detail. We outline the physical mechanisms by which electrokinetic effects (streaming potentials) are generated. We investigate the potential impact of the electrical field on the passage of albumin across the glomerular filtration barrier. We review the mathematical heteroporous model including electrical effects and analyse a selection of experimental studies for indications that electrical effects influence glomerular permeability significantly.
aChair of Molecular Pharmacology, University Hospital of RWTH Aachen University
bInstitute for Numerical Mathematics, RWTH Aachen University, Aachen
cMax Planck Institute of Colloids and Interfaces, Science Park Golm, Potsdam
dDepartment of Nephrology and Clinical Immunology, University Hospital of RWTH Aachen University, Aachen, Germany
Correspondence to Marcus J. Moeller, MD, Department of Nephrology and Clinical Immunology, RWTH University Hospital Aachen, Pauwels street 30, 52074 Aachen, Germany. Tel: +49 241 8089530; fax: +49 241 8082446; e-mail: email@example.com