title: Augmented sphingosylphosphorylcholine-induced Ca2+-sensitization of mesenteric artery contraction in spontaneously hypertensive rat.
abstract: Sphingosylphosphorylcholine (SPC) is a vasoconstricting lysosphingolipid, and the RhoA/Rho-kinase pathway plays an important role in SPC-induced contraction. Since RhoA/Rho-kinase-mediated signaling is involved in the generation and/or maintenance of hypertension, we compared the effect of SPC on the contractility of endothelium-denuded small mesenteric arteries in spontaneously hypertensive rats (SHR) and Wistar Kyoto rats (WKY). Fura-2 Ca2+ signals, contractile responses, and phosphorylation of 20-kDa myosin light chains (MLC20) were measured. Ten microM SPC induced a gradual and sustained vasoconstriction, which was greater in arteries of the SHR (82.5 +/- 4.3%, n=9) than in those of the WKY (26.7 +/- 4.5%, n=10). In Ca2+-free media, SPC gradually increased vascular tone in the SHR, but caused little vasoconstriction in the WKY. In the SHR and WKY, SPC evoked a greater vasoconstriction than did high K+ depolarization at a given Ca2+ ratio, and the Ca2+ ratio-tension curve induced by SPC was significantly shifted to the left compared with that induced by high K+ depolarization. However, the magnitude of shift to the left was greater in the SHR than in the WKY. The Rho-kinase inhibitor Y-27632 significantly inhibited SPC-induced contractions, but neither the protein kinase C inhibitor calphostin-C nor PD98059, which inhibits activation of some mitogen-activated protein kinases, had any effect on the SHR or the WKY. SPC significantly increased the phosphorylation of MLC20 in both the SHR and the WKY, and Y-27632 inhibited the SPC-induced increase in MLC(20) phosphorylation in the SHR. Our results suggest that SPC induces greater vascular tone in the SHR than in the WKY. Furthermore, our results indicate that activation of the Rho-kinase pathway plays an important role in the SPC-induced Ca2+ sensitization in the SHR.
authors.affiliation: Department of Physiology, College of Medicine, Yonsei University, C.P.O. Box 8044, Seoul, 120-752, South Korea.
authors.forename: Sung-Kyung
authors.initials: SK
authors.lastname: Ryu
authors.forename: Duck Sun
authors.initials: DS
authors.lastname: Ahn
authors.forename: Young-Eun
authors.initials: YE
authors.lastname: Cho
authors.forename: Soo-Kyung
authors.initials: SK
authors.lastname: Choi
authors.forename: Young-Hwan
authors.initials: YH
authors.lastname: Kim
authors.forename: Kathleen G
authors.initials: KG
authors.lastname: Morgan
authors.forename: Young-Ho
authors.initials: YH
authors.lastname: Lee
mesh_terms: D000577:Amides / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D005419:Flavonoids / Q000494:pharmacology; D006973:Hypertension / Q000503:physiopathology*; D008638:Mesenteric Arteries / Q000187:drug effects* / Q000502:physiology; D020928:Mitogen-Activated Protein Kinases / Q000502:physiology; D018994:Myosin Light Chains / Q000378:metabolism; D009281:Naphthalenes / Q000494:pharmacology; D010766:Phosphorylation; D010767:Phosphorylcholine / Q000031:analogs & derivatives* / Q000494:pharmacology; D011493:Protein Kinase C / Q000502:physiology; D011725:Pyridines / Q000494:pharmacology; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000494:pharmacology; D014661:Vasoconstriction / Q000187:drug effects*; D054460:rho-Associated Kinases / Q000502:physiology
chemical_list: D000577:Amides; D005419:Flavonoids; D018994:Myosin Light Chains; D009281:Naphthalenes; D011725:Pyridines; C005356:sphingosine phosphorylcholine; D010767:Phosphorylcholine; C108830:Y 27632; D054460:rho-Associated Kinases; D011493:Protein Kinase C; D020928:Mitogen-Activated Protein Kinases; C058819:calphostin C; D013110:Sphingosine; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one; D002118:Calcium