Electrical forces determine glomerular permeability.
There is ongoing controversy about the mechanisms that determine the characteristics of the glomerular filter. Here, we tested whether flow across the glomerular filter generates extracellular electrical potential differences, which could be an important determinant of glomerular filtration. In micropuncture experiments in Necturus maculosus, we measured a potential difference across the glomerular filtration barrier that was proportional to filtration pressure (-0.045 mV/10 cm H₂O). The filtration-dependent potential was generated without temporal delay and was negative within Bowman's space. Perfusion with the cationic polymer protamine abolished the potential difference. We propose a mathematical model that considers the relative contributions of diffusion, convection, and electrophoretic effects on the total flux of albumin across the filter. According to this model, potential differences of -0.02 to -0.05 mV can induce electrophoretic effects that significantly influence the glomerular sieving coefficient of albumin. This model of glomerular filtration has the potential to provide a mechanistic theory, based on experimental data, about the filtration characteristics of the glomerular filtration barrier. It provides a unique approach to the microanatomy of the glomerulus, renal autoregulation, and the pathogenesis of proteinuria.
Molecular Pharmacology, University Hospital of Rheinisch Westfälische Technische Hochschule (RWTH) Aachen University, Aachen, Germany.
Ralf
R
Hausmann
Christoph
C
Kuppe
Herbert
H
Egger
Frank
F
Schweda
Volker
V
Knecht
Marlies
M
Elger
Sylvia
S
Menzel
Douglas
D
Somers
Gerald
G
Braun
Astrid
A
Fuss
Sandra
S
Uhlig
Wilhelm
W
Kriz
George
G
Tanner
Jürgen
J
Floege
Marcus J
MJ
Moeller
D000818:Animals; D001693:Biological Transport, Active; D002463:Cell Membrane Permeability / Q000502:physiology*; D004195:Disease Models, Animal; D017097:Electric Impedance; D050533:Glomerular Basement Membrane / Q000378:metabolism / Q000502:physiology*; D005919:Glomerular Filtration Rate; D006801:Humans; D007674:Kidney Diseases / Q000503:physiopathology; D007678:Kidney Glomerulus / Q000098:blood supply / Q000502:physiology*; D008564:Membrane Potentials / Q000502:physiology*; D009338:Necturus maculosus; D017597:Renal Blood Flow, Effective / Q000502:physiology