Sphingosylphosphorylcholine induces Ca2+-sensitization of vascular smooth muscle contraction: possible involvement of Rho-kinase

Sphingosylphosphorylcholine (SPC), a sphingolipid, concentration-dependentl y (1-50 mu M) induced contraction and slight elevation of the cytosolic Ca2 + concentration ([Ca2+](i)) in smooth muscle of the pig coronary artery, th e result being a marked increase in the force/[Ca2+](i) ratio. In alpha-tox in- or beta-escin-permeabilized, but not Triton X-100-permeabilized, vascul ar strips, SPC induced contraction at constant [Ca2+](i) (pCa 6.3) in the a bsence of GTP, whereas a G-protein-coupled receptor agonist, histamine, req uired the presence of GTP to induce the contraction. The Rho-kinase blocker , Y-27632 (10 mu M) abolished the SPC-induced Ca2+-sensitization, without a ffecting the Ca2+-induced contraction. These results suggest that SPC induc es Ca2+-sensitization of force in vascular smooth muscle, presumably throug h the activation of Rho-kinase (or a related kinase), (C) 2000 Federation o f European Biochemical Societies. Published ba Elsevier Science B.V. All ri ghts reserved,