Mechanism of Endothelin-1–Induced Contraction in Rabbit Basilar Artery

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Abstract
Background and Purpose—Endothelin-1 (ET-1) is suggested to be a major cause of cerebral vasospasm after subarachnoid hemorrhage. However, the mechanism of ET-1–induced contraction in cerebral arteries remains unclear. This study was undertaken to demonstrate the possible role of protein tyrosine kinase (PTK), mitogen-activated protein kinase (MAPK), and protein kinase C (PKC) in ET-1–induced contraction. Methods—PD-98059, damnacanthal, wortmannin, AG-490, genistein, calphostin C, and staurosporine were used to inhibit, or relax, the ET-1–induced contraction of basilar artery, studied with an isometric tension system. Immunoprecipitation of MAPK in ET-1–stimultated rings of basilar artery without or with the above inhibitors was studied with Western blot. Results—(1) ET-1 produced concentration-dependent contraction and MAPK immunoprecipitation in rabbit basilar artery by activation of ETA but not ETB receptors. (2) MAPK inhibitors PD-98059 and U-0126 produced dose-dependent inhibition of ET-1–induced contraction. (3) The Src tyrosine kinase inhibitor damnacanthal, the phosphatidylinositol-3 kinase inhibitor wortmannin, and the Janus tyrosine kinase2 inhibitor AG-490 abolished ET-1–induced contraction. (4) The PKC inhibitor staurosporine but not calphostin C abolished ET-1–induced contraction, and the PTK inhibitor genistein partially reduced ET-1–induced contraction. (5) In arteries precontracted by ET-1, PD-98059, U-0126, wortmannin, AG-490, genistein, and staurosporine produced concentration-dependent relaxation. (6) ET-1 induced a biphasic and time-dependent MAPK immunoprecipitation. (7) PD-98059, U-0126, genistein, AG-490, and damnacanthal, but not staurosporine or wortmannin, abolished the effect of ET-1 on MAPK immunoreactivity. Conclusions—This study demonstrated that MAPK may be involved in ET-1–induced contraction in rabbit basilar artery. MAPK is downstream of PTK, Src, and Janus tyrosine kinase pathways but may not be downstream of phosphatidylinositol-3 kinase pathways. The possible involvement of PKC in ET-1–induced contraction requires further investigation. Inhibition of these pathways may offer alternative treatment for ET-1–induced contraction and cerebral vasospasm.