The Na+/H+ Exchanger Present in Trout Erythrocyte Membranes is Not Responsible for the Amiloride-insensitive Na+/Li+ Exchange Activity

The Na+/H+ Exchanger Present in Trout Erythrocyte Membranes is Not Responsible for the... The protein responsible for the Na+/Li+ exchange activity across the erythrocyte membrane has not been cloned or isolated. It has been suggested that a Na+/H+ exchanger could be responsible for the Na+/Li+ exchange activity across the erythrocyte membrane. Previously, we reported that in the trout erythrocyte, the Li+/H+ exchange activity (mediated by the Na+/H+ exchanger βNHE) and the Na+/Li+ exchange activity respond differently to cAMP, DMA (dimethyl-amiloride) and O2. We concluded that the DMA insensitive Na+/Li+ exchange activity originates from a different protein. To further examine these findings, we measured Li+ efflux in fibroblasts expressing the βNHE as the only Na+/H+ exchanger. Moreover, the internal pH of these cells was monitored with a fluorescent probe. Our findings indicate that acidification of fibroblasts expressing the Na+/H+ exchanger βNHE, induces a Na+ stimulated Li+ efflux activity in trout erythrocytes. This exchange activity, however, is DMA sensitive and therefore differs from the DMA insensitive Na+/Li+ exchange activity. In these fibroblasts no significant DMA insensitive Na+/Li+ exchange activity was found. These results support the hypothesis that the trout erythrocyte Na+/Li+ exchange activity is not mediated by the Na+/H+ exchanger (βNHE) present in these membranes. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png The Journal of Membrane Biology Springer Journals

The Na+/H+ Exchanger Present in Trout Erythrocyte Membranes is Not Responsible for the Amiloride-insensitive Na+/Li+ Exchange Activity

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Publisher
Springer-Verlag
Copyright
Copyright © Inc. by 1997 Springer-Verlag New York
Subject
Life Sciences; Biochemistry, general; Human Physiology
ISSN
0022-2631
eISSN
1432-1424
D.O.I.
10.1007/s002329900308
Publisher site
See Article on Publisher Site

Abstract

The protein responsible for the Na+/Li+ exchange activity across the erythrocyte membrane has not been cloned or isolated. It has been suggested that a Na+/H+ exchanger could be responsible for the Na+/Li+ exchange activity across the erythrocyte membrane. Previously, we reported that in the trout erythrocyte, the Li+/H+ exchange activity (mediated by the Na+/H+ exchanger βNHE) and the Na+/Li+ exchange activity respond differently to cAMP, DMA (dimethyl-amiloride) and O2. We concluded that the DMA insensitive Na+/Li+ exchange activity originates from a different protein. To further examine these findings, we measured Li+ efflux in fibroblasts expressing the βNHE as the only Na+/H+ exchanger. Moreover, the internal pH of these cells was monitored with a fluorescent probe. Our findings indicate that acidification of fibroblasts expressing the Na+/H+ exchanger βNHE, induces a Na+ stimulated Li+ efflux activity in trout erythrocytes. This exchange activity, however, is DMA sensitive and therefore differs from the DMA insensitive Na+/Li+ exchange activity. In these fibroblasts no significant DMA insensitive Na+/Li+ exchange activity was found. These results support the hypothesis that the trout erythrocyte Na+/Li+ exchange activity is not mediated by the Na+/H+ exchanger (βNHE) present in these membranes.

Journal

The Journal of Membrane BiologySpringer Journals

Published: Dec 1, 1997

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