Sodium pumps in the Malpighian tubule of Rhodnius sp.

• Main Author: CARUSO-NEVES,CELSO
• Publication Date: 2000
• Other Authors: LOPES,ANÍBAL GIL
• Format: Article
• Language: eng
• Source: Anais da Academia Brasileira de Ciências (Online)
• Download full: http://old.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652000000300014
• topic: Malpighian tubule; (Na+ + K+)ATPase; Na+ -ATPase; fluid secretion; adenosine; 5-hydroxitryptamine

Malpighian tubule of Rhodnius sp. express two sodium pumps: the classical ouabain-sensitive (Na+ + K+)ATPase and an ouabain-insensitive, furosemide-sensitive Na+-ATPase. In insects, 5-hydroxitryptamine is a diuretic hormone released during meals. It inhibits the (Na+ + K+)ATPase and Na+ -ATPase activities indicating that these enzymes are involved in fluid secretion. Furthermore, in Rhodnius neglectus, proximal cells of Malpighian tubule exposed to hyperosmotic medium, regulate their volume through a mechanism called regulatory volume increase. This regulatory response involves inhibition of the (Na+ + K+)ATPase activity that could lead to accumulation of active osmotic solute inside the cell, influx of water and return to the normal cell volume. Adenosine, a compound produced in stress conditions, also inhibits the (Na+ + K+)ATPase activity. Taken together these data indicate that (Na+ + K+)ATPase is a target of the regulatory mechanisms of water and ions transport responsible for homeostasis in Rhodnius sp.