Urea Inhibits the Na-K Pump in Human Erythrocytes

Urea Inhibits the Na-K Pump in Human Erythrocytes Recent studies have established that urea alters the activity of several volume-sensitive cation transport pathways. However, it has remained unclear whether urea has any effect on transport pathways that are not volume-sensitive. We examined the effect of urea on Na-K pump in the human erythrocytes. In cells from nine subjects, 500 mm urea inhibited 52 ± 10% of the pump activity measured as the ouabain-sensitive (OS) K influx. Urea inhibited the OS K influx reversibly, in a concentration-dependent manner. [3H] oubain binding, a measure of the number of Na-K pump sites remained unchanged with urea. Urea decreased the V max for ouabain-sensitive K influx, but did not alter the apparent K m for external K. Furthermore, urea did not alter the apparent K m for intracellular Na. The ion turnover per pump site was decreased in the presence of urea. Thus, physiologically relevant urea concentration inhibit the Na-K pump in human erythrocyte. The inhibition of the Na-K pump by urea suggests that the effects of urea may not be limited to volume-sensitive transporters, but may be more widespread. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png The Journal of Membrane Biology Springer Journals

Urea Inhibits the Na-K Pump in Human Erythrocytes

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Publisher
Springer-Verlag
Copyright
Copyright © Inc. by 1998 Springer-Verlag New York
Subject
Life Sciences; Biochemistry, general; Human Physiology
ISSN
0022-2631
eISSN
1432-1424
D.O.I.
10.1007/s002329900426
Publisher site
See Article on Publisher Site

Abstract

Recent studies have established that urea alters the activity of several volume-sensitive cation transport pathways. However, it has remained unclear whether urea has any effect on transport pathways that are not volume-sensitive. We examined the effect of urea on Na-K pump in the human erythrocytes. In cells from nine subjects, 500 mm urea inhibited 52 ± 10% of the pump activity measured as the ouabain-sensitive (OS) K influx. Urea inhibited the OS K influx reversibly, in a concentration-dependent manner. [3H] oubain binding, a measure of the number of Na-K pump sites remained unchanged with urea. Urea decreased the V max for ouabain-sensitive K influx, but did not alter the apparent K m for external K. Furthermore, urea did not alter the apparent K m for intracellular Na. The ion turnover per pump site was decreased in the presence of urea. Thus, physiologically relevant urea concentration inhibit the Na-K pump in human erythrocyte. The inhibition of the Na-K pump by urea suggests that the effects of urea may not be limited to volume-sensitive transporters, but may be more widespread.

Journal

The Journal of Membrane BiologySpringer Journals

Published: Sep 15, 1998

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