Cytoskeleton elements mediate the inhibition of the (Na++K+)atpase activity by PKC in Rhodnius prolixus malpighian tubules during hyperosmotic shock.
In a previous paper, we observed that the specific activity of (Na++K+)ATPase of the isolated Malpighian tubules from Rhodnius prolixus is inhibited by protein kinase C (PKC) during hyperosmotic shock [Arenstein et al., J Membr Biol 146:47-57 [1995]; Caruso-Neves et al., Z Naturforsch 53c:911-917 [1998]). In the present paper, we study the involvement of the cytoskeleton in this process using isolated Malpighian tubules of Rhodnius prolixus. We observed that pre-incubation of the Malpighian tubule cells in hyperosmotic media decreases the specific activity of (Na++K+)ATPase by 90%. This effect was completely reversed when colchicine, which disrupts microtubules, or cytochalasin B, an inhibitor of actin microfilament polymerization, were added to the media in a dose-dependent manner. The maximal reversion was obtained with colchicine 7.0 microM or cytochalasin B 5.0 microM. The simultaneous addition of sphingosine 50 ng/mL, an inhibitor of PKC, to 10 microM colchicine or 5 microM cytochalasin B, in hyperosmotic media, did not change the stimulatory effect of these drugs on the specific activity of (Na++K+)ATPase. On the other hand, the co-incubation of TPA 20 ng/mL, an activator of PKC, to colchicine or cytochalasin B within hyperosmotic media, abolished the stimulatory effect of these drugs on the specific activity of (Na++K+)ATPase to a similar extent as hyperosmotic shock. These results suggest that inhibition of the (Na++K+)ATPase of the isolated Malpighian tubules from Rhodnius prolixus by PKC during hyperosmotic shock is mediated by cytoskeletal elements.
Caruso-Neves
C
C
Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Brazil.
Silva
I V
IV
Morales
M M
MM
Lopes
A G
AG
D000818:Animals; D003078:Colchicine / Q000494:pharmacology; D003571:Cytochalasin B / Q000494:pharmacology; D003599:Cytoskeleton / Q000201:enzymology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D008317:Malpighian Tubules / Q000187:drug effects / Q000201:enzymology*; D009997:Osmotic Pressure; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D020064:Reduviidae / Q000187:drug effects / Q000201:enzymology*; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors*; D013110:Sphingosine / Q000494:pharmacology
D004791:Enzyme Inhibitors; D003571:Cytochalasin B; D011493:Protein Kinase C; D000254:Sodium-Potassium-Exchanging ATPase; D013110:Sphingosine; D003078:Colchicine