Albumin and glucose effects on cell growth parameters, albumin uptake and Na(+)/H(+)-exchanger Isoform 3 in OK cells.
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.[1]References
- 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, B., Gekle, M., Poronnik, P., Pollock, C. Cell. Physiol. Biochem. (2003) [Pubmed]
Annotations and hyperlinks in this abstract are from individual authors of WikiGenes or automatically generated by the WikiGenes Data Mining Engine. The abstract is from MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.About WikiGenesOpen Access LicencePrivacy PolicyTerms of Useapsburg
