Sphingosylphosphorylcholine induces Ca(2+)-sensitization of vascular smooth muscle contraction: possible involvement of rho-kinase

Sphingosylphosphorylcholine (SPC), a sphingolipid, concentration-dependently (1-50 microM) induced contraction and slight elevation of the cytosolic Ca(2+) concentration ([Ca(2+)](i)) in smooth muscle of the pig coronary artery, the result being a marked increase in the force/[Ca(2+)](i) ratio. In alpha-toxin- or beta-escin-permeabilized, but not Triton X-100-permeabilized, vascular strips, SPC induced contraction at constant [Ca(2+)](i) (pCa 6.3) in the absence of GTP, whereas a G-protein-coupled receptor agonist, histamine, required the presence of GTP to induce the contraction. The Rho-kinase blocker, Y-27632 (10 microM) abolished the SPC-induced Ca(2+)-sensitization, without affecting the Ca(2+)-induced contraction. These results suggest that SPC induces Ca(2+)-sensitization of force in vascular smooth muscle, presumably through the activation of Rho-kinase (or a related kinase).