AJP - Renal Physiology, Vol 268, Issue 5 972-F979, Copyright © 1995 by American Physiological Society
Capillary network structure does not affect theoretical analysis of glomerular size selectivity
A. Remuzzi and B. Ene-Iordache
Biomedical Engineering Laboratory, Mario Negri Institute for Pharmacological Research, Bergamo, Italy.
Anatomical studies have demonstrated that the glomerular capillaries are
complex and heterogeneous networks. Conventional models of glomerular size
selectivity, however, are based on the assumption of simplified geometries.
We developed a theoretical model of glomerular size-selective function
based on the geometric data obtained in a previous reconstruction of a
glomerular network from a normal Munich-Wistar rat. This heterogeneous
model was compared with the homogeneous model conventionally used to
calculate membrane selective parameters from the fractional clearance of
two test solutes, neutral dextran and Ficoll. For both models we assumed a
hypothetical log-normal distribution of pore sizes and calculated optimal
membrane pore-size parameters using previously published values of
fractional clearances. The difference between the sieving coefficients
calculated with the two models was negligible, never exceeding 5.5%. Since
the homogeneous model does not consider the pressure drop along the
glomerular capillary, we also computed fractional clearances with the
homogeneous model, assuming the same pressure drop as in the heterogeneous
one. The differences in computed fractional clearances using the
homogeneous model with and without a pressure drop were less than 1.2%. We
concluded that models based on identical capillary networks can therefore
be used for interpreting sieving coefficients for macromolecules.
