A gel-membrane model of glomerular charge and size selectivity in series.
We have analyzed glomerular sieving data from humans, rats in vivo, and from isolated perfused rat kidneys (IPK) and present a unifying hypothesis that seems to resolve most of the conflicting results that exist in the literature. Particularly important are the data obtained in the cooled IPK, because they allow a variety of experimental conditions for careful analysis of the glomerular barrier; conditions that never can be obtained in vivo. The data strongly support the classic concept of a negative charge barrier, but separate components seem to be responsible for charge and size selectivity. The new model is composed of a dynamic gel and a more static membrane layer. First, the charged gel structure close to the blood compartment has a charge density of 35-45 meq/l, reducing the concentration of albumin to 5-10% of that in plasma, due to ion-ion interactions. Second, the size-selective structure has numerous functional small pores (radius 45-50 A) and far less frequent large pores (radius 75-115 A), the latter accounting for 1% of the total hydraulic conductance. Both structures are required for the maintenance of an intact glomerular barrier.
Ohlson
M
M
Department of Physiology, Göteborg University, Göteborg 405 30, Sweden.
Sörensson
J
J
Haraldsson
B
B
D000818:Animals; D002199:Capillary Permeability; D004594:Electrophysiology; D005782:Gels; D066298:In Vitro Techniques; D007678:Kidney Glomerulus / Q000098:blood supply / Q000378:metabolism / Q000502:physiology*; D008566:Membranes; D008954:Models, Biological; D051381:Rats
D005782:Gels