Survey of osmolytes in renal cell lines

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Abstract
In renal medullas during antidiuresis, the extracellular fluid is hyperosmotic because of high concentrations of NaCl and urea. Under those conditions, the cells contain high concentrations of organic osmolytes, namely sorbitol, myo-inositol, glycerophosphorylcholine (GPC), and betaine to balance the extracellular hyperosmolality. These organic osmolytes increase cell osmolality without perturbing the intracellular milieu in ways that would degrade the function of cellular macromolecules. The present study surveyed a number of cell lines for the ability to survive in media with high concentrations of NaCl and/or urea and for the accumulation of organic osmolytes. Of the renal cell lines tested, MDCK, GRB-MAL1, and A6 cells proliferated in hyperosmotic media, but medullary interstitial cells LLC-PK1 and LLC-PK3 did not proliferate, nor did nonrenal HTC-BH cells, MDCK, LLC-PK1, and LLC-PK3 cells contained higher concentrations of myo-inositol, GPC, and betaine when cultured in media containing high NaCl (with or without high urea) and much lower or undetectable levels of these osmolytes when grown in isosmotic media. Sorbitol, and to a lesser extent myo-inositol, were elevated in GRB-MAL1 cells in media hyperosmotic with NaCl but not in isosmotic media. There was less accumulation of organic osmolytes when only urea was added to increase osmolality. Thus the same osmolytes were accumulated by one or another cell line in vitro as were previously found in renal medullas. These cell lines provide models for studying osmolyte accumulation.