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      Acute and Chronic Effects of Hyperosmolality on mRNA and Protein Expression and the Activity of Na-K-ATPase in the IMCD

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          We investigated acute and chronic effects of hyperosmolality on mRNA and protein expressions of Na-K-ATPase α and β isoforms and Na-K-ATPase activity in the rat inner medullary collecting duct (IMCD). Incubation of IMCD in hypertonic medium for 30 min reduced the Na-K-ATPase activity by 50%. The Na-K-ATPase activity of dehydrated rats measured in isotonic medium was decreased, and incubation in hypertonic medium did not further decrease the activity. Incubation of IMCD in hypertonic medium for 6 h did not change α<sub>1</sub> mRNA. In contrast, dehydration decreased α<sub>1</sub> subunit mRNA and protein and β<sub>1</sub> protein expressions without changing β<sub>1</sub> mRNA. These data show (1) that acute hyperosmolality decreases Na-K-ATPase activity in IMCD without changing α<sub>1</sub> and β<sub>1</sub> mRNA and (2) that 2 days of dehydration decreased Na-K-ATPase activity by reducing α<sub>1</sub> and β<sub>1</sub> proteins. Thus, the mechanisms for the inhibition of the Na-K-ATPase activity in IMCD is defferent between acute and chronic exposure to hyperosmolality.

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          Author and article information

          Nephron Exp Nephrol
          Cardiorenal Medicine
          S. Karger AG
          August 1999
          26 July 1999
          : 7
          : 4
          : 295-305
          a2nd Department of Internal Medicine,Tokyo Medical and Dental University, Tokyo; b3rd Department of Internal Medicine, Kumamoto University School of Medicine, Kumamoto, Japan
          20617 Exp Nephrol 1999;7:295–305
          © 1999 S. Karger AG, Basel

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          Page count
          Figures: 12, References: 31, Pages: 11
          Self URI (application/pdf): https://www.karger.com/Article/Pdf/20617
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