Kidney international
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Kidney international · Mar 2009
Interstitial tonicity controls TonEBP expression in the renal medulla.
Cells in the hyperosmotic kidney medulla, express a transcriptional activator termed tonicity responsive enhancer binding protein (TonEBP). Genes targeted by TonEBP protect kidney cells from the deleterious effects of hyperosmolality by inducing the expression of organic osmolytes and molecular chaperones, and other genes that mediate urine concentration such as aquaporin-2 and urea transporters. We tested here the effect of hypertonicity and hyperosmotic salt in the renal medullary interstitium on the expression TonEBP. ⋯ Here, TonEBP expression was blunted in the outer and inner medulla which was due, in part, to decreased mRNA abundance. As expected, the expression of TonEBP target genes in the renal medulla also decreased in response to furosemide. Hence TonEBP expression in the renal medulla is stimulated by interstitial hypertonicity.
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Recent studies indicate that serum cystatin C is a better marker of glomerular filtration rate (GFR) and is a stronger predictor of cardiovascular disease and mortality than serum creatinine. Before cystatin C can gain wide acceptance, information about factors that affect generation, elimination, and analysis is needed. Stevens et al. analyze non-GFR-related factors associated with cystatin C and creatinine levels. The results will be useful in interpreting cystatin C levels in research and clinical practice.