Angiotensin II induces tyrosine phosphorylation of insulin receptor substrate 1 and its association with phosphatidylinositol 3-kinase in rat heart.
We have investigated whether angiotensin II (AII) is able to induce insulin receptor substrate 1 (IRS-1) phosphorylation and its association with phosphatidylinositol 3-kinase (PI 3-kinase) in the rat heart in vivo. The phosphorylation state of IRS-1 following infusion of insulin or AII via the vena cava was assessed after immunoprecipitation with an anti-peptide antibody to IRS-1 followed by immunoblotting with an anti-phosphotyrosine antibody and an anti-PI 3-kinase antibody. Densitometry indicated a 5.6 +/- 1.3-fold increase in IRS-1 phosphorylation after stimulation with AII and a 12.8 +/- 3.1-fold increase after insulin. The effect was maximal at an AII concentration of 10(-8) M and occurred 1 min after infusion. There was also a 6.1 +/- 1.2-fold increase in IRS-1-associated PI 3-kinase in response to AII. In the isolated perfused heart the result was similar, showing a direct effect of AII on this pathway. When the animals were pretreated for 1 h with DuP 753, a non-peptide AII-receptor 1 (AT1 receptor) antagonist, there was a marked reduction in the AII-induced tyrosine phosphorylation of IRS-1, suggesting that phosphorylation is initially mediated by the AT1 receptor. We conclude that AII stimulates tyrosine phosphorylation of IRS-1 and its association with PI 3-kinase. This pathway thus represents an additional signalling mechanism stimulated by AII in the rat heart in vivo.
Saad
M J
MJ
Department of Internal Medicine, FCM, UNICAMP Campinas, SP, Brazil.
Velloso
L A
LA
Carvalho
C R
CR
D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D004591:Electrophoresis, Polyacrylamide Gel; D015151:Immunoblotting; D066298:In Vitro Techniques; D007328:Insulin / Q000494:pharmacology*; D055504:Insulin Receptor Substrate Proteins; D008297:Male; D008970:Molecular Weight; D009206:Myocardium / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases; D010750:Phosphoproteins / Q000302:isolation & purification / Q000378:metabolism*; D010766:Phosphorylation; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism*; D019000:Phosphotyrosine / Q000378:metabolism*; D051381:Rats; D014443:Tyrosine / Q000378:metabolism
D007328:Insulin; D055504:Insulin Receptor Substrate Proteins; C526296:Irs1 protein, rat; D010750:Phosphoproteins; D000804:Angiotensin II; D019000:Phosphotyrosine; D014443:Tyrosine; D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor)