title: Endothelin-1 receptor antagonist: effects on endothelin- and cyclosporine-treated mesangial cells.
abstract: Endothelin-1 (Et) has profound effects on glomerular microcirculation and mesangial cell contraction. A parameter of mesangial cell contraction was examined by measuring myosin light chain phosphorylation (MLCP) in glomerular mesangial cells in the presence and absence of a newly developed endothelin-1 receptor antagonist (EtA). Addition of Et alone (10 nM) caused a marked increase in MLCP, which, on average, rose by 53 +/- 6% above the level in cells exposed to vehicle (P less than 0.0005). This effect was shown to continue for at least one hour; MLCP at 60 minutes was 64 +/- 12% higher than controls, (P less than 0.025), constituting a unique observation of an in vitro parameter which parallels the characteristic in vivo effect of Et. Treatment of cells with EtA virtually abolished this Et-induced increase in MLCP, which rose by only 2 +/- 3% and -1 +/- 4% for doses of EtA of 44 nM and 66 nM, respectively. Examination of the intracellular calcium concentration, [Ca2+]i, revealed that EtA almost completely abolished the transient increase in [Ca2+]i evoked by Et and also suppressed the early portions of the sustained increase in [Ca2+]i. EtA was ineffective in abolishing [Ca2+]i increase in response to arginine vasopressin. Finally, to evaluate EtA's efficacy in a pathophysiologic setting, we also studied mesangial cells exposed to cyclosporine (Cs). Exposure of mesangial cells to Cs (10(-5) M) for 60 minutes caused a significant increase in MLCP, on average, by 38 +/- 6% above control (P less than 0.0005), while cells exposed to Cs in the presence of EtA increased MLCP significantly less, by only 15 +/- 9%. These data provide further evidence for Et's long-lasting cellular actions, and demonstrate inhibitory effects of an Et receptor antagonist after direct cellular exposure to Et and also after Cs exposure, a pathophysiologic setting which likely involves Et.
authors.affiliation: Department of Pediatrics, Vanderbilt University School of Medicine, Nashville, Tennessee.
authors.forename: M
authors.initials: M
authors.lastname: Takeda
authors.forename: M D
authors.initials: MD
authors.lastname: Breyer
authors.forename: T D
authors.initials: TD
authors.lastname: Noland
authors.forename: T
authors.initials: T
authors.lastname: Homma
authors.forename: R L
authors.initials: RL
authors.lastname: Hoover
authors.forename: T
authors.initials: T
authors.lastname: Inagami
authors.forename: V
authors.initials: V
authors.lastname: Kon
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D016572:Cyclosporine / Q000494:pharmacology*; D003600:Cytosol / Q000378:metabolism; D016232:Endothelins / Q000494:pharmacology*; D005920:Glomerular Mesangium / Q000187:drug effects* / Q000378:metabolism; D008969:Molecular Sequence Data; D009218:Myosins / Q000378:metabolism; D010456:Peptides, Cyclic / Q000737:chemistry / Q000494:pharmacology; D010766:Phosphorylation; D011956:Receptors, Cell Surface / Q000037:antagonists & inhibitors*; D017466:Receptors, Endothelin; D014661:Vasoconstriction / Q000187:drug effects
chemical_list: D016232:Endothelins; D010456:Peptides, Cyclic; D011956:Receptors, Cell Surface; D017466:Receptors, Endothelin; D016572:Cyclosporine; D009218:Myosins; C072247:cyclo(Trp-Asp-Pro-Val-Leu); D002118:Calcium