Vasorelaxing effect of the Rho-kinase inhibitor, Y-27632, in isolated canine basilar arteries.
OBJECTIVE
Increased calcium sensitization mediated by Rho/Rho-kinase may be important in the pathogenesis of cerebral vasospasm. The effects of a highly selective Rho-kinase inhibitor, Y-27632, were investigated on spasmogen-induced contractions of canine basilar artery.


METHODS
Typical spasmogenic substances present after subarachnoid hemorrhage (SAH), including prostaglandin F2a (PGF2a), 12-deoxyphorbol 13-isobutyrate (DPB), sphingosylpho-sphorylcholine (SPC) and high K+, were used in the study. Isometric tension was recorded in canine basilar artery rings in vitro. Intracellular calcium concentration ([Ca2+]i) and contraction force were measured simultaneously in fura-2-loaded canine basilar artery strips. The myosin light chain (MLC) phosphorylation levels were measured by glycerol gel electrophoresis followed by Western blotting.


RESULTS
Isometric tension recording revealed that the Rho-kinase inhibitor, Y-27632, dose-dependently inhibited vasocontraction induced by PGF2a and SPC, but not that induced by DPB. Simultaneous recordings of [Ca2+]i and tension revealed that the vasorelaxing effect of Y-27632 was not associated with changes in [Ca2+]i, suggesting that Y-27632 may inhibit calcium sensitization. Vasocontraction induced by DPB was not inhibited by Y-27632, but was inhibited by staurosporine. Phosphorylation of MLC was increased by PGF2a and SPC, and significantly inhibited by Y-27632, whereas such phosphorylation was increased by DPB, but not significantly inhibited by Y-27632.


CONCLUSIONS
Several spasmogenic mediators released after SAH may cause vasospasm through Rho-kinase-mediated increase in calcium sensitization. Rho-kinase inhibitors, including Y-27632, may be effective for the prevention of cerebral vasospasm after SAH.
Hashiba
Yasuhiro
Y
Department of Neurosurgery, Gunma University Graduate School of Medicine, 3-39-22 Showa-machi, Maebashi, Gunma 371-8511, Japan. nshashi@showa.gunma-u.ac.jp
Tosaka
Masahiko
M
Saito
Nobuhito
N
Imai
Hideaki
H
Shimizu
Tatsuya
T
Sasaki
Tomio
T
D000577:Amides / Q000494:pharmacology*; D000818:Animals; D001488:Basilar Artery / Q000187:drug effects*; D002118:Calcium / Q000378:metabolism; D015237:Dinoprost / Q000494:pharmacology; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D066298:In Vitro Techniques; D018994:Myosin Light Chains / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D010767:Phosphorylcholine / Q000031:analogs & derivatives / Q000494:pharmacology; D011725:Pyridines / Q000494:pharmacology*; D013110:Sphingosine / Q000031:analogs & derivatives / Q000494:pharmacology; D014664:Vasodilation / Q000187:drug effects*