Angiotensin II regulates vascular smooth muscle cell ph, contraction, and growth via tyrosine kinase dependent signaling pathways

Touyz, R.M. and Schiffrin, E.L. (1997) Angiotensin II regulates vascular smooth muscle cell ph, contraction, and growth via tyrosine kinase dependent signaling pathways. Hypertension, 30(2), pp. 222-229. (doi: 10.1161/01.HYP.30.2.222)

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Angiotensin II (Ang II), a potent vasoactive peptide with mitogenic potential, influences vascular smooth muscle cell contraction and growth through receptor-linked pathways that increase intracellular free Ca2+ concentration ([Ca2+]i) and pH (pHi). Activation of these second messengers by Ang II may involve tyrosine kinase-dependent signaling pathways. This study determined the role of tyrosine kinases in Ang II–stimulated pHi, and in simultaneously measured contractile and [Ca2+]i responses, as well as growth in cultured vascular smooth muscle cells from mesenteric arteries of Wistar-Kyoto rats. pHi was determined by fluorescent digital imaging using 2′,7′-bis(2-carboxyethyl)-5(6)-carboxyfluorescein acetoxymethyl ester (BCECF-AM). Vascular smooth muscle cell [Ca2+]i and contractile responses were assessed simultaneously by fura 2 methodology and by photomicroscopy in cells grown on rat tail collagen gels. Cell growth was determined by DNA and protein synthesis as measured by [3H]thymidine and [3H]leucine incorporation, respectively. The Ang II receptor subtypes (AT1 or AT2) through which Ang II mediates effects were assessed with [Sar1,Ile8]Ang II (a nonselective subtype antagonist), losartan (a selective AT1 antagonist), and PD 123319 (a selective AT2 antagonist). To determine whether tyrosine kinases influence Ang II–stimulated responses, cells were pretreated with 10−5 mol/L tyrphostin A-23 (a specific tyrosine kinase inhibitor). Ang II increased pHi in a dose-dependent manner (pD2, 9.2±0.2) and significantly increased vascular smooth muscle cell contraction (30%) and [Ca2+]i (pD2, 7.4±0.1). Ang II (10−7 mol/L) increased DNA ([3H]thymidine incorporation) and protein synthesis ([3H]leucine incorporation). [Sar1,Ile8]Ang II and losartan but not PD 123319 abolished Ang II–elicited responses. Tyrphostin A-23 significantly attenuated Ang II–stimulated pHi responses; it also inhibited [Ca2+]i and contractile responses and cell growth. The inactive analogue tyrphostin A-1 did not alter Ang II–stimulated actions. These results provide novel evidence for a role of tyrosine kinases in Ang II–mediated pHi responses in vascular smooth muscle cells and indicate that tyrosine kinases participate in the regulation of signal transduction associated with AT1 receptor subtype–mediated contraction and growth.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Touyz, Professor Rhian
Authors: Touyz, R.M., and Schiffrin, E.L.
College/School:College of Medical Veterinary and Life Sciences > Institute of Cardiovascular and Medical Sciences
Journal Name:Hypertension
Publisher:American Heart Association
ISSN (Online):1524-4563

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