title: Role of endogenous ENaC and TRP channels in the myogenic response of rat posterior cerebral arteries.
abstract: OBJECTIVE
  Mechanogated ion channels are predicted to mediate pressure-induced myogenic vasoconstriction in small resistance arteries. Recent findings have indicated that transient receptor potential (TRP) channels and epithelial sodium channels (ENaC) are involved in mechanotransduction. The purpose of this study was to investigate the role of TRP channels and ENaC in the myogenic response. Our previous study suggested that ENaC could be a component of the mechanosensitive ion channels in rat posterior cerebral arteries (PCA). However, the specific ion channel proteins mediating myogenic constriction are unknown. Here we found, for the first time, that ENaC interacted with TRPM4 but not with TRPC6 using immunoprecipitation and confocal microscopy.
  
  
  RESULTS
  Treatment with a specific βENaC inhibitor, amiloride, a specific TRPM4 inhibitor, 9-phenanthrol, and a TRPC6 inhibitor, SKF96365, resulted in inhibition of the pressure-induced myogenic response. Moreover, the myogenic response was inhibited in rat PCA transfected with small interfering RNA of βENaC, TRPM4, and TRPC6. Co-treatment with amiloride and 9-phenanthrol showed a similar inhibitory effect on myogenic contraction compared to single treatment with amiloride or 9-phenanthrol. The myogenic response was not affected by 9-phenanthrol or amiloride treatment in PCA transfected with βENaC or TRPM4 siRNA, respectively. However, pressure-induced myogenic response was fully inhibited by co-treatment with amiloride, 9-phenanthrol, and SKF96365, and by treatment with SKF96365 in PCA transfected with βENaC siRNA.
  
  
  CONCLUSIONS
  Our results suggest that ENaC, TRPM4, and TRPC6 play important roles in the pressure-induced myogenic response, and that ENaC and TRPM4 interact in rat PCA.
authors.affiliation: Department of Physiology, College of Medicine, Brain Korea 21 PLUS Project for Medical Science, Yonsei University, Seoul, Korea.
authors.forename: Eok-Cheon
authors.initials: EC
authors.lastname: Kim
authors.affiliation: Department of Physiology, College of Medicine, Brain Korea 21 PLUS Project for Medical Science, Yonsei University, Seoul, Korea.
authors.forename: Soo-Kyoung
authors.initials: SK
authors.lastname: Choi
authors.affiliation: Department of Physiology, College of Medicine, Brain Korea 21 PLUS Project for Medical Science, Yonsei University, Seoul, Korea.
authors.forename: Mihwa
authors.initials: M
authors.lastname: Lim
authors.affiliation: Department of Physiology, College of Medicine, Brain Korea 21 PLUS Project for Medical Science, Yonsei University, Seoul, Korea.
authors.forename: Soo-In
authors.initials: SI
authors.lastname: Yeon
authors.affiliation: Department of Physiology, College of Medicine, Brain Korea 21 PLUS Project for Medical Science, Yonsei University, Seoul, Korea.
authors.forename: Young-Ho
authors.initials: YH
authors.lastname: Lee
mesh_terms: D000584:Amiloride; D000818:Animals; D001794:Blood Pressure / Q000502:physiology*; D053503:Epithelial Sodium Channels / Q000378:metabolism*; D006439:Hemodynamics / Q000502:physiology*; D007093:Imidazoles; D010616:Phenanthrenes; D020769:Posterior Cerebral Artery / Q000502:physiology*; D034741:RNA, Small Interfering; D051381:Rats; D050053:TRPM Cation Channels / Q000378:metabolism*
chemical_list: D053503:Epithelial Sodium Channels; D007093:Imidazoles; D010616:Phenanthrenes; D034741:RNA, Small Interfering; D050053:TRPM Cation Channels; C500239:TRPM4 protein, rat; D000584:Amiloride; C091375:9-phenanthrol; C063159:1-(2-(3-(4-methoxyphenyl)propoxy)-4-methoxyphenylethyl)-1H-imidazole