title: Constriction of retinal arterioles to endothelin-1: requisite role of rho kinase independent of protein kinase C and L-type calcium channels.
abstract: OBJECTIVE
  Although endothelin-1 (ET-1) is a potent vasoconstrictor peptide implicated in several retinal pathologies, the underlying mechanism of vasoconstriction is understood incompletely. We addressed this issue by assessing the contributions of extracellular calcium (Ca²⁺), L-type voltage-operated calcium channels (L-VOCCs), Rho kinase (ROCK), and protein kinase C (PKC) to ET-1-induced constriction of porcine retinal arterioles, all of which have been implicated commonly in vascular smooth muscle contraction.
  
  
  METHODS
  Porcine retinal arterioles (~50-100 μm) were isolated for vasomotor study and molecular assessment of ROCK isoforms.
  
  
  RESULTS
  Isolated arterioles developed stable basal tone at 55 cmH₂O luminal pressure and constricted to ET-1 (0.1 nM) with a 40 ± 6% reduction in resting diameter in 20 minutes. In the absence of extraluminal Ca²⁺, arterioles lost basal tone and failed to constrict to ET-1. Although L-VOCC inhibitor nifedipine reduced basal tone and blocked vasoconstriction to PKC activator PDBu, vasoconstriction to ET-1 was unaffected. The broad-spectrum PKC inhibitor Gö-6983 abolished vasoconstriction to PDBu, but did not alter ET-1-induced vasoconstriction or basal tone. Incubation of arterioles with ROCK inhibitor H-1152 abolished basal tone and vasoconstrictions to ET-1 and PDBu. Both ROCK1 and ROCK2 isoforms were expressed in the retinal arteriolar wall.
  
  
  CONCLUSIONS
  Extracellular Ca²⁺ entry via L-VOCCs and basal ROCK activity play important roles in the maintenance of basal tones of porcine retinal arterioles. ET-1-induced constriction is mediated by extracellular Ca²⁺ entry independent of L-VOCCs and by ROCK activation without the involvement of PKC. However, direct PKC activation can cause vasoconstriction via L-VOCC and ROCK signaling.
authors.affiliation: Department of Systems Biology and Translational Medicine, College of Medicine, Texas A&M Health Science Center, Temple, Texas, USA.
authors.forename: Luke B
authors.initials: LB
authors.lastname: Potts
authors.forename: Yi
authors.initials: Y
authors.lastname: Ren
authors.forename: Guangrong
authors.initials: G
authors.lastname: Lu
authors.forename: Enoch
authors.initials: E
authors.lastname: Kuo
authors.forename: Ellen
authors.initials: E
authors.lastname: Ngo
authors.forename: Lih
authors.initials: L
authors.lastname: Kuo
authors.forename: Travis W
authors.initials: TW
authors.lastname: Hein
mesh_terms: D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D001160:Arterioles / Q000502:physiology*; D015153:Blotting, Western; D002118:Calcium / Q000502:physiology; D002121:Calcium Channel Blockers / Q000494:pharmacology; D020746:Calcium Channels, L-Type / Q000502:physiology*; D019332:Endothelin-1 / Q000494:pharmacology*; D004730:Endothelium, Vascular / Q000502:physiology; D007150:Immunohistochemistry; D007211:Indoles / Q000494:pharmacology; D008301:Maleimides / Q000494:pharmacology; D009543:Nifedipine / Q000494:pharmacology; D020033:Protein Isoforms; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000502:physiology*; D012039:Regional Blood Flow / Q000502:physiology; D012161:Retinal Artery / Q000502:physiology*; D013552:Swine; D014661:Vasoconstriction / Q000502:physiology; D054460:rho-Associated Kinases / Q000037:antagonists & inhibitors / Q000502:physiology
chemical_list: C465664:2-(1-(3-dimethylaminopropyl)-5-methoxyindol-3-yl)-3-(1H-indol-3-yl)maleimide; C459092:2-methyl-1-((4-methyl-5-isoquinolinyl)sulfonyl)homopiperazine; D002121:Calcium Channel Blockers; D020746:Calcium Channels, L-Type; D019332:Endothelin-1; D007211:Indoles; D008301:Maleimides; D020033:Protein Isoforms; D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D054460:rho-Associated Kinases; D011493:Protein Kinase C; D009543:Nifedipine; D002118:Calcium