Affiliation:
1. Departments of Nephrology and
2. Department of Physiology, University of Bergen, N-5509 Bergen, Norway
3. Clinical Chemistry, University Hospital, S-221 85 Lund, Sweden; and
Abstract
The size and charge-selective properties of the glomerular barrier are partly controversial. Glomerular sieving coefficients (θ) for proteins have rarely been determined noninvasively before in vivo. Therefore, θ was assessed vs. glomerular filtration rate (GFR;51Cr-EDTA clearance) in intact rats for radiolabeled myoglobin, κ-dimer, neutral horseradish peroxidase (nHRP), neutral human serum albumin (nHSA), and native albumin (HSA). To obtain θ, glomerular tracer clearance, assessed from the 7- to 8-min kidney uptake of protein, was divided by the GFR. The data were fitted with a two-pore model of glomerular permeability, where the small-pore radius was 37.35 ± 1.11 (SE) Å, and the “unrestricted pore area over diffusion path length” ( A0/Δ X) 1.84 ± 0.43 · 106cm. Although seemingly horizontal for nHRP and nHSA, the log θ vs. GFR curves showed slightly negative slopes for the proteins investigated in the GFR interval of 2–4.5 ml/min. Strong negative (linear) correlations between (log) θ and GFR were obtained for myoglobin ( P = 0.002) and HSA ( P = 0.006), whereas they were relatively weak for nHRP and nHSA and nonsignificant for κ-dimer. θ for nHSA was markedly higher than that for HSA. In conclusion, there were no indications of increases in θ vs. GFR, as indicative of concentration polarization, for the proteins investigated at high GFRs. Furthermore, the glomerular small-pore radius assessed from endogenous (neutral) protein sieving data was found to be smaller than previously determined using dextran or Ficoll as test molecules.
Publisher
American Physiological Society
Cited by
116 articles.
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