title: Vascular tone and Ca(2+) signaling in murine cremaster muscle arterioles in vivo.
abstract: OBJECTIVE
  We sought to determine some of the molecular requirements for basal state "tone" of skeletal muscle arterioles in vivo, and whether asynchronous Ca(2+) waves are involved or not.
  
  
  METHODS
  Cremaster muscles of anesthetized exMLCK and smGCaMP2 biosensor mice were exteriorized, and the fluorescent arterioles were visualized with wide-field, confocal or multiphoton microscopy to observe Ca(2+) signaling and arteriolar diameter.
  
  
  RESULTS
  Basal state tone of the arterioles was ~50%. Local block of Ang-II receptors (AT1 ) or α1 -adrenoceptors (α1 -AR) had no effect on diameter, nor did complete block of sympathetic nerve activity (SNA). Inhibition of phospholipase C caused dilation nearly to the Ca(2+) -free (passive) diameter, as did exposure to nifedipine or 2-APB. Arterioles were also dilated when treated with SKF96365. High-resolution imaging of exMLCK fluorescence (ratio) or GCaMP2 fluorescence in smooth muscle cells failed to reveal Ca(2+) waves (although Ca(2+) waves/transients were readily detected by both biosensors in small arteries, ex vivo).
  
  
  CONCLUSIONS
  Arterioles of cremaster muscle have vascular tone of ~ 50%, which is not due to α1 -AR, AT1 R, or SNA. PLC activity, L-type Ca(2+) channels, 2-APB- and SKF96365-sensitive channels are required. Propagating Ca(2+) waves are not present. A key role for PLC and InsP3 R in vascular tone in vivo, other than producing Ca(2+) waves, is suggested.
authors.affiliation: Department of Physiology, School of Medicine, University of Maryland Baltimore, Baltimore, Maryland 21201, USA.
authors.forename: Joseph R H
authors.initials: JR
authors.lastname: Mauban
authors.forename: Joseph
authors.initials: J
authors.lastname: Zacharia
authors.forename: Jin
authors.initials: J
authors.lastname: Zhang
authors.forename: Withrow Gil
authors.initials: WG
authors.lastname: Wier
mesh_terms: D000818:Animals; D001160:Arterioles / Q000166:cytology / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism; D020013:Calcium Signaling / Q000502:physiology*; D051379:Mice; D008822:Mice, Transgenic; D036641:Microscopy, Fluorescence, Multiphoton; D018482:Muscle, Skeletal / Q000098:blood supply* / Q000166:cytology
chemical_list: D015220:Calcium Channels; D002118:Calcium