title: Involvement of the Gi/o/cGMP/PKG pathway in the AT2-mediated inhibition of outer cortex proximal tubule Na+-ATPase by Ang-(1-7).
abstract: The molecular mechanisms involved in the Ang-(1-7) [angiotensin-(1-7)] effect on sodium renal excretion remain to be determined. In a previous study, we showed that Ang-(1-7) has a biphasic effect on the proximal tubule Na+-ATPase activity, with the stimulatory effect mediated by the AT1 receptor. In the present study, we investigated the molecular mechanisms involved in the inhibition of the Na+-ATPase by Ang-(1-7). All experiments were carried out in the presence of 0.1 nM losartan to block the AT1 receptor-mediated stimulation. In this condition, Ang-(1-7) at 0.1 nM inhibited the Na+-ATPase activity of the proximal tubule by 54%. This effect was reversed by 10 nM PD123319, a specific antagonist of the AT2 receptor, and by 1 muM GDP[beta-S] (guanosine 5'-[beta-thio]diphosphate), an inhibitor of G protein. Ang-(1-7) at 0.1 M induced [35S]GTP[S] (guanosine 5'-[gamma-[35S]thio]triphosphate) binding and 1 mug/ml pertussis toxin, an inhibitor of G(i/o) protein, reversed the Ang-(1-7) effect. Furthermore, it was observed that the inhibitory effect of Ang-(1-7) on the Na+-ATPase activity was completely reversed by 0.1 microM LY83583, an inhibitor of guanylate cyclase, and by 2 muM KT5823, a PKG (protein kinase G) inhibitor, and was mimicked by 10 nM d-cGMP (dibutyryl cGMP). Ang-(1-7) increased the PKG activity by 152% and this effect was abolished by 10 nM PD123319 and 0.1 microM LY83583. Taken together, these data indicate that Ang-(1-7) inhibits the proximal tubule Na+-ATPase by interaction with the AT2 receptor that subsequently activates the G(i/o) protein/cGMP/PKG pathway.
authors.affiliation: Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, CCS-bloco G, 21949-900, Rio de Janeiro, RJ, Brazil.
authors.forename: Lucienne da Silva
authors.initials: Lda S
authors.lastname: Lara
authors.forename: Fabíola
authors.initials: F
authors.lastname: Cavalcante
authors.forename: Flavia
authors.initials: F
authors.lastname: Axelband
authors.forename: Aloa Machado
authors.initials: AM
authors.lastname: De Souza
authors.forename: Anibal Gil
authors.initials: AG
authors.lastname: Lopes
authors.forename: Celso
authors.initials: C
authors.lastname: Caruso-Neves
mesh_terms: D000251:Adenosine Triphosphatases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D000803:Angiotensin I / Q000494:pharmacology*; D057912:Angiotensin II Type 2 Receptor Blockers; D000818:Animals; D027682:Cation Transport Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D006152:Cyclic GMP / Q000378:metabolism*; D017869:Cyclic GMP-Dependent Protein Kinases / Q000378:metabolism*; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000378:metabolism*; D007672:Kidney Cortex / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D007687:Kidney Tubules, Proximal / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D010446:Peptide Fragments / Q000494:pharmacology*; D044139:Receptor, Angiotensin, Type 2 / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D013552:Swine
chemical_list: D057912:Angiotensin II Type 2 Receptor Blockers; D027682:Cation Transport Proteins; D010446:Peptide Fragments; D044139:Receptor, Angiotensin, Type 2; D000803:Angiotensin I; D017869:Cyclic GMP-Dependent Protein Kinases; D000251:Adenosine Triphosphatases; C021838:sodium-translocating ATPase; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; D006152:Cyclic GMP; C118790:angiotensin I (1-7)