Osmotic Modulation of the Ouabain-Sensitive (Na++K+)ATPase from Malpighian Tubules of Rhodnius prolixus
The presence and regulation by hyperosmotic medium of the ouabain-sensitive (Na +K )ATPase of the Malpighian tubule cells of Rhodnius prolixus was investigated. The ouabain-sensitive (Na +K )ATPase activity was 5.4 ± 0.5 nmol Pi x mg x min . Vanadate 100 μM completely abolished this ATPase activity....
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Published in | Zeitschrift für Naturforschung C. A journal of biosciences Vol. 53; no. 9; pp. 911 - 917 |
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Main Authors | , , |
Format | Journal Article |
Language | English |
Published |
Verlag der Zeitschrift für Naturforschung
01.10.1998
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Subjects | |
Online Access | Get full text |
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Summary: | The presence and regulation by hyperosmotic medium of the ouabain-sensitive (Na
+K
)ATPase of the Malpighian tubule cells of Rhodnius prolixus was investigated. The ouabain-sensitive (Na
+K
)ATPase activity was 5.4 ± 0.5 nmol Pi x mg
x min
. Vanadate 100 μM completely abolished this ATPase activity. In hyperosmotic medium, obtained by addition of 180 mᴍ mannitol, the (Na
+K
)ATPase activity was inhibited by 60%. When the cell lysates were preincubated in hyperosmotic medium for 30 minutes and the ATPase activity was assayed in isosmotic medium, the (Na
+K
)ATPase activity was not modified. Addition of 50 ng/ml sphingosine, a protein kinase C inhibitor, abolished the inhibition of (Na
+K
)ATPase activity in hyperosmotic medium. Furtherm ore, phorbol ester (TPA), an activator of protein kinase C, mimicked the effect of hyperosmotic shock on (Na
+K
)ATPase activity. The increase in Ca
concentration decreased the (Na
+K
)ATPase activity by 60% in isosmotic medium, with maximal effect obtained in 10
m Ca
. No effect was observed in hyperosmotic medium. The inhibitory effect of Ca
on the (Na
+K
)ATPase was not reversed by sphingosine. These results indicate that the ouabain-sensitive (Na
+K
) ATPase activity of the Malpighian tubule is regulated by both increasing Ca
concentration and by the osmolality of the medium by different and integrative ways. |
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ISSN: | 0939-5075 1865-7125 |
DOI: | 10.1515/znc-1998-9-1021 |