title: TRPV2 Channels Contribute to Stretch-Activated Cation Currents and Myogenic Constriction in Retinal Arterioles.
abstract: OBJECTIVE
  Activation of the transient receptor potential channels, TRPC6, TRPM4, and TRPP1 (PKD2), has been shown to contribute to the myogenic constriction of cerebral arteries. In the present study we sought to determine the potential role of various mechanosensitive TRP channels to myogenic signaling in arterioles of the rat retina.
  
  
  METHODS
  Rat retinal arterioles were isolated for RT-PCR, Fura-2 Ca2+ microfluorimetry, patch-clamp electrophysiology, and pressure myography studies. In some experiments, confocal immunolabeling of wholemount preparations was used to examine the localization of specific mechanosensitive TRP channels in retinal vascular smooth muscle cells (VSMCs).
  
  
  RESULTS
  Reverse transcription-polymerase chain reaction analysis demonstrated mRNA expression for TRPC1, M7, V1, V2, V4, and P1, but not TRPC6 or M4, in isolated retinal arterioles. Immunolabeling revealed plasma membrane, cytosolic and nuclear expression of TRPC1, M7, V1, V2, V4, and P1 in retinal VSMCs. Hypoosmotic stretch-induced Ca2+ influx in retinal VSMCs was reversed by the TRPV2 inhibitor tranilast and the nonselective TRPP1/V2 antagonist amiloride. Inhibitors of TRPC1, M7, V1, and V4 had no effect. Hypoosmotic stretch-activated cation currents were similar in Na+ and Cs+ containing solutions suggesting no contribution by TRPP1 channels. Direct plasma membrane stretch triggered cation current activity that was blocked by tranilast and specific TRPV2 pore-blocking antibodies and mimicked by the TRPV2 activator, Δ9-tetrahydrocannabinol. Preincubation of retinal arterioles with TRPV2 blocking antibodies prevented the development of myogenic tone.
  
  
  CONCLUSIONS
  Our results suggest that retinal VSMCs express a range of mechanosensitive TRP channels, but only TRPV2 appears to contribute to myogenic signaling in this vascular bed.
authors: Centre for Experimental Medicine, Queen's University of Belfast, Belfast, United Kingdom.
authors: Mary K
authors: MK
authors: McGahon
authors: Centre for Experimental Medicine, Queen's University of Belfast, Belfast, United Kingdom.
authors: José A
authors: JA
authors: Fernández
authors: Centre for Experimental Medicine, Queen's University of Belfast, Belfast, United Kingdom.
authors: Durga P
authors: DP
authors: Dash
authors: Centre for Experimental Medicine, Queen's University of Belfast, Belfast, United Kingdom.
authors: Jon
authors: J
authors: McKee
authors: Centre for Experimental Medicine, Queen's University of Belfast, Belfast, United Kingdom.
authors: David A
authors: DA
authors: Simpson
authors: Institute of Biology, Taras Shevchenko National University of Kyiv, Kyiv, Ukraine.
authors: Alex V
authors: AV
authors: Zholos
authors: Centre for Experimental Medicine, Queen's University of Belfast, Belfast, United Kingdom.
authors: J Graham
authors: JG
authors: McGeown
authors: Centre for Experimental Medicine, Queen's University of Belfast, Belfast, United Kingdom.
authors: Tim M
authors: TM
authors: Curtis
mesh_terms: D000818:Animals; D001160:Arterioles / Q000502:physiology*; D005786:Gene Expression Regulation; D007150:Immunohistochemistry; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000502:physiology*; D018408:Patch-Clamp Techniques; D012313:RNA / Q000235:genetics*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012161:Retinal Artery / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D050916:TRPV Cation Channels / Q000378:metabolism*; D014661:Vasoconstriction / Q000235:genetics*
chemical_list: D050916:TRPV Cation Channels; C476722:Trpv2 protein, rat; D012313:RNA