The normal kidney filters nephrotic levels of albumin retrieved by proximal tubule cells: Retrieval is disrupted in nephrotic states

L. M. Russo, R. M. Sandoval, M. McKee, T. M. Osicka, A. B. Collins, D. Brown, Bruce Molitoris, W. D. Comper

Research output: Contribution to journalArticle

282 Citations (Scopus)

Abstract

The origin of albuminuria remains controversial owing to difficulties in quantifying the actual amount of albumin filtered by the kidney. Here we use fluorescently labeled albumin, together with the powerful technique of intravital 2-photon microscopy to show that renal albumin filtration in non-proteinuric rats is ∼50 times greater than previously measured and is followed by rapid endocytosis into proximal tubule cells (PTCs). The endocytosed albumin appears to undergo transcytosis in large vesicles (500 nm in diameter), identified by immunogold staining of endogenous albumin by electron microscopy, to the basolateral membrane where the albumin is disgorged back to the peritubular blood supply. In nephrotic rats, the rate of uptake of albumin by the proximal tubule (PT) is decreased. This is consistent with reduced expression of clathrin, megalin, and vacuolar H+-ATPase A subunit, proteins that are critical components of the PT endocytotic machinery. These findings strongly support the paradigm-shifting concept that the glomerular filter normally leaks albumin at nephrotic levels. Albuminuria does not occur as this filtered albumin load is avidly bound and retrieved by PTCs. Dysfunction of this retrieval pathway leads to albuminuria. Thus, restoration of the defective endocytotic and processing function of PT epithelial cells might represent an effective strategy to limit urinary albumin loss, at least in some types of nephrotic syndrome.

Original languageEnglish
Pages (from-to)504-513
Number of pages10
JournalKidney International
Volume71
Issue number6
DOIs
StatePublished - Mar 13 2007

Fingerprint

Albumins
Kidney
Albuminuria
Endocytosis
Low Density Lipoprotein Receptor-Related Protein-2
Vacuolar Proton-Translocating ATPases
Transcytosis
Clathrin
Protein Subunits
Nephrotic Syndrome
Photons
Microscopy
Electron Microscopy
Epithelial Cells
Staining and Labeling
Membranes

Keywords

  • Albuminuria
  • Glomerular filtration barrier
  • Nephropathy
  • Pathophysiology of renal disease and progression
  • Proximal tubule

ASJC Scopus subject areas

  • Nephrology

Cite this

Russo, L. M., Sandoval, R. M., McKee, M., Osicka, T. M., Collins, A. B., Brown, D., ... Comper, W. D. (2007). The normal kidney filters nephrotic levels of albumin retrieved by proximal tubule cells: Retrieval is disrupted in nephrotic states. Kidney International, 71(6), 504-513. https://doi.org/10.1038/sj.ki.5002041

The normal kidney filters nephrotic levels of albumin retrieved by proximal tubule cells : Retrieval is disrupted in nephrotic states. / Russo, L. M.; Sandoval, R. M.; McKee, M.; Osicka, T. M.; Collins, A. B.; Brown, D.; Molitoris, Bruce; Comper, W. D.

In: Kidney International, Vol. 71, No. 6, 13.03.2007, p. 504-513.

Research output: Contribution to journalArticle

Russo, L. M. ; Sandoval, R. M. ; McKee, M. ; Osicka, T. M. ; Collins, A. B. ; Brown, D. ; Molitoris, Bruce ; Comper, W. D. / The normal kidney filters nephrotic levels of albumin retrieved by proximal tubule cells : Retrieval is disrupted in nephrotic states. In: Kidney International. 2007 ; Vol. 71, No. 6. pp. 504-513.
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