Abstract
α2-Adrenoceptors potentiate vascular responses to angiotensin II. The goal of this study was to test the hypothesis that the phospholipase C (PLC)/protein kinase C (PKC)/c-src/phosphatidylinositol 3-kinase (PI3K) pathway contributes to the vascular angiotensin II/α2-adrenoceptor interaction. In rats in vivo, intrarenal infusions of angiotensin II (10 ng/kg/min) increased renal vascular resistance by 5.8 ± 0.5 units, and this response was enhanced (p < 0.05) to 9.1 ± 1.2 units by UK-14,304 [5-bromo-N-(4,5-dihydro-1H-imidazol-2-yl)-6-quinoxalinamine; 3 μg/kg/min; α2-adrenoceptor agonist]. Intrarenal infusions of U-73122 [1-[6-[[(17β)-3-methoxyestra-1,3,5(10)-trien-17-yl]amino]-hexyl]-1H-pyrrole-2,5-dione; 3 μg/min; PLC inhibitor], GF109203X [bisindolylmaleimide I; 10 μg/min; PKC inhibitor], CGP77675 [1-(2-{4-[4-amino-5-(3-methoxyphenyl)pyrrolo[2,3-d]pyrimidin-7-yl]phenyl}ethyl)piperidin-4-ol; 5 μg/min; c-src inhibitor], and wortmannin (1 μg/min; PI3K inhibitor) abolished the angiotensin II/α2-adrenoceptor interaction. In isolated perfused rat kidneys, angiotensin II (0.3, 1, and 3 nM) increased perfusion pressure (by 15 ± 8, 39 ± 4, and 93 ± 9 mm Hg, respectively), and UK-14,304 (1 μM) potentiated these responses (to 36 ± 4, 67 ± 7, and 135 ± 17 mm Hg, respectively). This angiotensin II/α2-adrenoceptor interaction was abolished by U-73122 (10 μM), GF109203X (3 μM), CGP77675 (5 μM), and wortmannin (0.2 μM). Preglomerular microvascular smooth muscle cells expressed phospholipase (PLC)-β2, PLC-β3, c-src, phospho(tyrosine 416)-c-src, and PI3K. In these cells, angiotensin II (0.1 μM) and UK-14,304 (1 μM) per se did not increase phospho-c-src; however, the combination of angiotensin II plus UK-14,304 doubled phospho-c-src, and this interaction was abolished by U-73122 (10 μM) and GF109203X (3 μM). In conclusion, the PLC/PKC/c-src/PI3K pathway may contribute importantly to the interaction between α2-adrenoceptors and angiotensin II on renal vascular resistance.
Footnotes
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This work was supported by National Institutes of Health Grant HL 69846.
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doi:10.1124/jpet.105.086074.
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ABBREVIATIONS: Ang II, angiotensin II; PLC, phospholipase C; PKC, protein kinase C; PI3K, phosphatidylinositol 3-kinase; MABP, mean arterial blood pressure; SHR, spontaneously hypertensive rat(s); RBF, renal blood flow; DMSO, dimethyl sulfoxide; RVR, renal vascular resistance; PGSMC, preglomerular microvascular smooth muscle cell; U-73122, 1-(6-((17β)-3-methoxyestra-1,3,5[10]-trien-17-yl)amino]hexyl)-1H-pyrrole-2,5-dione; GF109203X, 2-[1-(3-dimethylaminopropyl)-1H-indol-3-yl]-3-(1H-indol-3-yl)maleimide; CGP77675, 1-(2-{4-[4-amino-5-(3-methoxyphenyl)pyrrolo[2,3-d]pyrimidin-7-yl]phenyl}ethyl)piperidin-4-ol; UK-14,304, 5-bromo-N-(4,5-dihydro-1H-imidazol-2-yl)-6-quinoxalinamine.
- Received March 9, 2005.
- Accepted May 17, 2005.
- The American Society for Pharmacology and Experimental Therapeutics
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