Sphingosylphosphorylcholine induces cytosolic Ca2+ elevation in endothelial cells in situ and causes endothelium-dependent relaxation through nitric oxide production in bovine coronary artery

Sphingosylphosphorylcholine (SPC) increased intracellular Ca2+ concentratio n ([Ca2+]i) and nitric oxide NO) production in endothelial cells in situ on bovine aortic valves, and induced endothelium-dependent relaxation of bovi ne coronary arteries precontracted with U-46619, The SPC-induced vasorelaxa tion was inhibited by NO-monomethyl-L-arginine, an inhibitor of both consti tutive and inducible NO synthase (NOS), but not by 1-(2-trifloromethylhenyl ) imidazole, an inhibitor of inducible NOS (iNOS). Immunoblotting revealed that endothelial constitutive NOS, but not iNOS, was present in endothelial cells in situ on the bovine aortic valves. We propose that SPC activates [ Ca2+]i levels and NO production of endothelial cells in situ, thereby causi ng an endotheliumdependent vasorelaxation, (C) 1999 Federation of European Biochemical Societies.