Angiotensin II-induced MAPK phosphorylation mediated by Ras and/or phospholipase C-dependent phosphorylations but not by protein kinase C phosphorylation in cultured rat vascular smooth muscle cells

Angiotensin II (Ang II) induces a rapid increase in mitogen-activated protein kinase (MAPK) activity through the Ang II type 1 receptor in cultured rat vascular smooth muscle cells (VSMCs). In the present study, we examined the effects of the phospholipase C (PLC) inhibitor U73122, the protein kinase C (PKC) inhibitor GF109203X, and the Ras inhibitor farnesylthiosalicylic acid (FTS) on Ang II-induced activation of p42/p44 MAPKs in cultured VSMCs. Phosphorylation was shown using the Western blot technique with specific phospho-antibodies against MAPK proteins. The PLC inhibitor U73122 abolished the Ang II-induced MAPK activity, while the PKC inhibitor GF109203X only decreased it. There was also an inhibition observed with the Ras inhibitor, FTS on Ang II-induced MAPK activity. These data suggest that Ang II-induced MAPK phosphorylation through the Ang II type 1 receptor could be mediated by Ras and/or PLC-dependent phosphorylations but not by PKC phosphorylation.