Sphingosine-1-phosphate and sphingosylphosphorylcholine constrict renal and mesenteric microvessels in vitro

1 Sphingolipids such as sphingosine-1-phosphate (SPP) and sphingosylphospho rylcholine (SPPC) can act both intracellularly and at G-protein-coupled rec eptors, some of which were cloned and designated as Edg-receptors. 2 Sphingolipid-induced vascular effects were determined in isolated rat mes enteric and intrarenal microvessels. Additionally, sphingolipid-induced ele vations in intracellular Ca2+ concentration were measured in cultured rat a ortic smooth muscle cells. 3 SPPC and SPP (0.1-100 mu mol l(-1)) caused concentration-dependent contra ction of mesenteric and intrarenal microvessels (e.g. SPPC in mesenteric mi crovessels pEC(50) 5.63+/-0.17 and E-max 49+/-3% of noradrenaline), with ot her sphingolipids being less active. The vasoconstrictor effect of SPPC in mesenteric microvessels was stereospecific (pEC(50) D-erythro-SPPC 5.69+/-0 .08, L-threo-SPPC 5.31+/-0.06) and inhibited by pretreatment with pertussis toxin (E-max from 44+/-5 to 19+/-4%), by chelation of extracellular Ca2+ w ith EGTA and by nitrendipine (E-max from 40+/-6 to 6+/-1 and 29+/-6%, respe ctively). Mechanical endothelial denudation or NO synthase inhibition did n ot alter the SPPC effects, while indomethacin reduced them (E-max from 87+/ -3 to 70+/-4%). 4 SPP and SPPC caused transient increases in intracellular Ca2+ concentrati ons in rat aortic smooth muscle cells in a pertussis toxin-sensitive manner . 5 Our data demonstrate that SPP and SPPC cause vasoconstriction of isolated rat microvessels and increase intracellular Ca2+ concentrations in culture d rat aortic smooth muscle cells. These effects appear to occur via recepto rs coupled to pertussis toxin-sensitive C-proteins. This is the first demon stration of effects of SPP and SPPC on vascular tone and suggests that sphi ngolipids may be an hitherto unrecognized class of endogenous regulators of vascular tone.