Adenine-induced inhibition of Na(+)-ATPase activity: Evidence for involvement of the Gi protein-coupled receptor in the cAMP signaling pathway.
In the present work, we demonstrate that adenine reduced Na(+)-ATPase activity in isolated basolateral membrane (BLM) of proximal tubule in a dose-dependent manner. Adenine metabolism was ruled out by TLC analysis of the potential [(3)H]adenine derived-metabolites. Specific binding of [(3)H]adenine to isolated BLM was observed in a dose-dependent manner with K(d) and B(max) of 242.6+/-27.6 nM and 2749.9+/-104.9 fmolmg(-1), respectively. Adenine increased the [(35)S]GTPgammaS specific binding and it was completely abolished by 10(-6)M GDPbetaS (G protein inhibitor) but it was not modified by DPCPX, DMPX and MRS1523, selective antagonists for A(1), A(2) and A(3) receptors, respectively. Furthermore, the inhibitory effect of adenine on the Na(+)-ATPase activity was blocked by 10(-6)M GDPbetaS, 1 microg/ml pertussis toxin (Gi protein inhibitor), 10(-6)M foskolin (adenylyl cyclase activator) and 10(-8)M cAMP. These data demonstrate that adenine inhibits the proximal tubule Na(+)-ATPase activity through the Gi protein-coupled receptor.
Wengert
M
M
Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, CCS Bloco G, 21949 Rio de Janeiro, RJ, Brazil.
Adão-Novaes
J
J
Assaife-Lopes
N
N
Leão-Ferreira
L R
LR
Caruso-Neves
C
C
D000225:Adenine / Q000008:administration & dosage*; D000251:Adenosine Triphosphatases / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D000818:Animals; D027682:Cation Transport Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism*; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D007687:Kidney Tubules, Proximal / Q000187:drug effects / Q000378:metabolism*; D043562:Receptors, G-Protein-Coupled / Q000378:metabolism*; D000254:Sodium-Potassium-Exchanging ATPase; D013552:Swine
D027682:Cation Transport Proteins; D043562:Receptors, G-Protein-Coupled; D000251:Adenosine Triphosphatases; C021838:sodium-translocating ATPase; D000254:Sodium-Potassium-Exchanging ATPase; D000225:Adenine