Albumin and glucose effects on cell growth parameters, Albumin uptake and Na+/H+-exchanger Isoform 3 in OK cells

Drumm, K, Lee, E, Stanners, S, Gassner, M, Gekle, P, Poronnik, P and Pollock, C 2003, 'Albumin and glucose effects on cell growth parameters, Albumin uptake and Na+/H+-exchanger Isoform 3 in OK cells', Cellular Physiology And Biochemistry, vol. 13, no. 4, pp. 199-206.


Document type: Journal Article
Collection: Journal Articles

Title Albumin and glucose effects on cell growth parameters, Albumin uptake and Na+/H+-exchanger Isoform 3 in OK cells
Author(s) Drumm, K
Lee, E
Stanners, S
Gassner, M
Gekle, P
Poronnik, P
Pollock, C
Year 2003
Journal name Cellular Physiology And Biochemistry
Volume number 13
Issue number 4
Start page 199
End page 206
Total pages 8
Publisher S. Karger AG
Abstract Background: The degree of albuminuria, the presence of sodium-dependent hypertension, and histological evidence of both tubular and interstitial pathology correlate with the progression of diabetic nephropathy. The sodium-hydrogen exchanger NHE-3 plays an integral role in both sodium reabsorption and receptor-mediated albumin endocytosis in proximal tubular cells (PTCs). The aim of this study was to investigate the direct effects of hyperglycemia and albumin on cell growth parameters, NHE-3 protein expression and albumin uptake in an in vitro model of PTCs. Methods: Opossum kidney (OK) cells were exposed to 5 mmol/l glucose (control) or 25 mmol/l (high) glucose in the presence or absence of either 0.1 or 1.0 g/l bovine serum albumin (BSA) for up to 72 hrs prior to study. 20 mmol/l mannitol + 5 mmol/l glucose was used as a control for hyperosmolality. The cell number, the degree of cell swelling, cell protein content and NHE-3 protein expression were assessed. Cellular albumin uptake and the role of NHE in both control and high glucose conditions were determined by FITC-BSA ± NHE-inhibitor ethyl isopropyl amiloride (EIPA). Results: High glucose and the hyperosmolar control induced cellular hypertrophy, which was not modified in the presence of albumin. Cell volume was initially increased by 1.0 g/l BSA, +/-high glucose, which normalized over 48-72 hrs. All experimental conditions induced an early and sustained increase in NHE-3 protein expression. High glucose increased albumin uptake, independent of changes in osmolality. EIPA reduced the albumin uptake in PTCs with kinetics supporting the role of NHE-3 in this process. Conclusion: These results suggest that exposure of PTCs to high glucose concentrations promotes osmolality mediated cell hypertrophy and increased tubular albumin reabsorption linked to an increase in NHE-3 expression. It is postulated that this increase in albumin uptake due to high glucose exposure may lead to proinflammatory protein overload of PTCs, ultimately impairing the compensatory increase in tubular albumin reabsorption.
Subject Cell Physiology
Keyword(s) animal cell
article
cation exchange
cell count
cell growth
cell strain
cell swelling
cell volume
controlled study
glucose intake
hyperglycemia
hyperosmolality
hyperosmolarity
hypertrophy
in vitro study
kidney cell
kinetics
nonhuman
osmolality
priority journal
protein expression
DOI - identifier 10.1159/000072422
Copyright notice Copyright © 2003 S. Karger AG, Basel.
ISSN 1015-8987
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