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|Title:||Regulation of insulin receptor substrate-2 tyrosine phosphorylation in animal models of insulin resistance|
|Author:||Rojas, F. A.|
Hirata, A. E.
|Abstract:||Insulin induces a wide variety of growth and metabolic responses in many cell types. These actions are initiated by insulin binding to its receptor and involve a series of alternative and complementary pathways created by the multiple substrates of the insulin receptor (insulin receptor substrates [IRSs]). We investigated IRS-1 and IRS-2 tyrosine phosphorylation; their association with phosphatidylinositol-3-OH kinase (M-K); and the phosphorylation of Akt, a serine-threonine kinase situated downstream of P13-K, in liver and muscle of two animal models of insulin resistance: epinephrine- or dexamethasone-treated rats. We used in vivo insulin infusion followed by tissue extraction, immunoprecipitation, and immunoblotting. IRS-1 and IRS-2 protein expression did not change in liver and muscle of the epinephrine-treated rats, but in dexamethasone-treated rats IRS-1 presented an increase in liver and a decrease in muscle tissue. P13-K and Akt protein expression did not change in liver or muscle of the two animal models of insulin resistance. There was a downregulation in insulin-induced IRS-1 and IRS-2 tyrosine phosphorylation and association with P13-K in both models of insulin resistance. In parallel, insulin-induced At phosphorylation was reduced in both tissues of epinephrine-treated rats, and in liver but not in muscle of dexamethasone-treated rats. The reduction in insulin-induced At phosphoryllation may help to explain the insulin resistance in liver and muscle of epinephrine-treated rats and in the liver of dexamethasone-treated rats|
|Citation:||Endocrine. Humana Press Inc, v. 21, n. 2, n. 115, n. 122, 2003.|
|Appears in Collections:||FCM - Artigos e Outros Documentos|
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