Attenuation of pressure-induced myogenic contraction and tyrosine phosphorylation by fasudil a cerebral vasodilator in rat cerebral artery

摘要

class="enumerated" style="list-style-type:decimal">The mechanism by which fasudil inhibits pressure-induced myogenic contraction was studied with regard to tyrosine phosphorylation in rat cerebral artery. Intracellular Ca²⁺ concentration ([Ca²⁺]i) and vessel diameter were simultaneously measured. Total tyrosine phosphorylation level and phosphorylation of tyrosine 419 on pp60^src required for its full catalytic activity were immunocytochemically detected in situ.Fasudil (1–100 μM) partially suppressed the increase in [Ca²⁺]i, and totally attenuated contraction elicited by pressurization from 10 to 60 mmHg. Furthermore, fasudil (100 μM) significantly attenuated tyrosine phosphorylation and the activity of pp60^src augmented in situ by pressure.Herbimycin A (1–100 nM) and genistein (3–30 μM), tyrosine kinase inhibitors, effectively attenuated the pressure-induced increase in [Ca²⁺]i, contraction, tyrosine phosphorylation, and activation of pp60^src. Both fasudil and herbimycin A directly inhibited the pp60^src activity in a cell free system.Orthovanadate (100 μM), a tyrosine phosphatase inhibitor, significantly potentiated the pressure-induced increase in [Ca²⁺]i and contraction.Nicardipine (100 nM), a Ca²⁺ antagonist, completely inhibited pressure-induced increase in [Ca²⁺]i and contraction, but affected neither tyrosine phosphorylation nor activity of pp60^src in the pressurized arteries.Arginine-glycine-aspartic acid-serine peptide (1–100 μM) concentration-dependently reduced the pressure-induced contraction.In addition to the hitherto reported vasodilatory actions of fasudil, the present results suggest the inhibition by fasudil of pressure-induced tyrosine phosphorylation and pp60^src activation. The wide spectrum of inhibitory actions of fasudil may contribute to the effective attenuation of the pressure-induced contraction in the cerebral artery.