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Organic osmolytes increase cytoplasmic viscosity in kidney cells
N Periasamy1, H P Kao, K Fushimi
1Department of Medicine, University of California, San Francisco 94143-0532.
The American Journal of Physiology
|October 1, 1992
Summary
Kidney cells accumulate osmolytes in high salt conditions, increasing internal viscosity. This hinders molecular movement within the cell, potentially slowing vital cellular processes.
Area of Science:
- Cell Physiology
- Renal Cell Biology
- Biophysics
Background:
- Kidney cells adapt to hyperosmolar environments by accumulating organic osmolytes.
- The impact of osmolyte accumulation on intracellular viscosity and solute mobility is not fully understood.
Purpose of the Study:
- To investigate how osmolyte accumulation in kidney cells affects the rotational and translational mobility of small polar solutes.
- To determine if increased intracellular viscosity is a consequence of osmolyte accumulation in renal cells.
Main Methods:
- Measured rotational mobility of BCECF using picosecond rotational correlation times (tau c) and multiharmonic microfluorimetry.
- Assessed translational mobility of BCECF via fluorescence photobleaching recovery.
- Utilized Madin-Darby canine kidney (MDCK) cells cultured in varying osmolarities (300-1,200 mosM).
Main Results:
- Cytosolic viscosity increased by up to 1.38-fold in MDCK cells grown in hyperosmolar media.
- Rotational correlation times (tau c) and apparent rotational viscosity (eta r) of BCECF increased with osmolyte accumulation.
- Translational mobility of BCECF significantly decreased in cells cultured in high osmolarity.
Conclusions:
- Accumulation of organic osmolytes in renal cells leads to significantly increased cytosolic viscosity.
- Elevated intracellular viscosity likely impedes enzymatic and transport processes within the cell.
- This study provides biophysical evidence for altered intracellular environments in response to osmotic stress.