Stimulation of the proximal tubule Na+-ATPase activity by adenosine A(2A) receptor.
The aim of this work was to determine the molecular mechanism involved in the stimulation of the pig kidney proximal tubule Na+-ATPase by adenosine (Ado). To study the role of A2 Ado receptors, we added in all experiments 10(-6)M DPCPX, an A1 receptor-selective antagonist, since we have previously shown that Ado inhibits the enzyme activity through this receptor. Ado increased the Na+-ATPase activity with maximal effect observed at 10(-6)M. The presence of both A(2A) and A(2B) receptors were demonstrated by immunoblotting using specific polyclonal antibodies. The stimulatory effect of Ado was completely abolished by 5 x 10(-9)M DMPX, an antagonist of A2 receptor, and 10(-7)M SCH 58261, an A(2A) receptor-selective antagonist. DMPA (10(-7)M), a specific agonist of A(2A) receptor mimicked the stimulatory effect of Ado. Involvement of a Gs protein/adenylate cyclase/PKA pathway was evidenced by: (a) the reversion of Ado-induced effect by GDPbetaS; (b) stimulation of the Na+-ATPase activity in a similar and non-additive manner to Ado by 10(-8)M cholera toxin, 10(-7)M GTPgammaS, 10(-6)M forskolin, 10(-7)M cAMP or 1.25 U catalytic subunit of PKA; (c) the reversion of the stimulatory effect of Ado by 10(-8)M PKA inhibitor peptide; (d) Ado-produced two-fold increase of the PKA activity, which was completely reversed by 10(-6)M DMPX. These are the first evidences showing the modulation of a renal primary active sodium transporter by Ado through A(2A) receptor.
Wengert
M
M
Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21949-900, RJ, Brazil.
Berto
C
C
Kaufman
J
J
Leão-Ferreira
L R
LR
Paes-de-Carvalho
R
R
Lopes
A G
AG
Caruso-Neves
C
C
D000241:Adenosine / Q000494:pharmacology*; D058917:Adenosine A2 Receptor Antagonists; D000814:Aniline Compounds / Q000494:pharmacology; D000818:Animals; D007687:Kidney Tubules, Proximal / Q000378:metabolism*; D043683:Receptors, Adenosine A2 / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*; D013552:Swine; D014665:Vasodilator Agents / Q000494:pharmacology*; D014970:Xanthines / Q000494:pharmacology
D058917:Adenosine A2 Receptor Antagonists; D000814:Aniline Compounds; D043683:Receptors, Adenosine A2; D014665:Vasodilator Agents; D014970:Xanthines; C050795:N,N-dimethyl-4-anisidine; C051360:1,3-dipropyl-8-cyclopentylxanthine; D000254:Sodium-Potassium-Exchanging ATPase; D000241:Adenosine