Sodium pumps in the Malpighian tubule of Rhodnius sp.
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.
Caruso-Neves
C
C
Laboratório de Fisiologia Renal, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, 21949-900, Brasil.
Lopes
A G
AG
D000818:Animals; D008317:Malpighian Tubules / Q000201:enzymology*; D012239:Rhodnius / Q000378:metabolism*; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors / Q000378:metabolism* / Q000502:physiology
D000254:Sodium-Potassium-Exchanging ATPase