title: Signal transduction in spontaneous myogenic tone in isolated arterioles from rat skeletal muscle.
abstract: OBJECTIVE
  The mechanism of spontaneous myogenic tone was investigated in isolated arteriolar segments.
  
  
  METHODS
  Arterioles were isolated from rat cremaster muscle. Segments were endothelium-denuded and mounted in a pressure myograph at 75 mmHg. Under this condition, segments spontaneously constricted from a passive diameter of 167 +/- 3 to 82 +/- 4 microns (n = 41). The effects of several inhibitors were tested on the maintenance of myogenic tone.
  
  
  RESULTS
  Gadolinium (10(-6)-10(-4) M), a putative inhibitor of stretch-activated cation channels, was ineffective. The phospholipase C (PLC) inhibitor 2-nitro-4-carboxyphenyl-N,N-diphenylcarbamate (NCDC) induced a dose-dependent inhibition of tone. NCDC inhibited phenylephrine- (10(-6) M), but not potassium buffer-induced (100 mM) constriction. The protein kinase C (PKC) inhibitors staurosporine, chelerythrine and calphostin C inhibited myogenic tone in a concentration-dependent manner. At an intermediate concentration, calphostin C selectively inhibited phenylephrine-induced constriction. However, all PKC inhibitors abolished responses to phenylephrine and potassium buffer at higher concentrations. The cytochrome P450 inhibitor 17-ODYA (0.3-3 x 10(-6) M) did not inhibit myogenic tone.
  
  
  CONCLUSIONS
  No evidence was found for a role of gadolinium-sensitive, stretch-activated cation channels or cytochrome P450 metabolites. On the other hand, both PLC and PKC contribute to the maintenance of myogenic tone.
mesh_terms: D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000470:Alkaloids; D000818:Animals; D001160:Arterioles; D053119:Benzophenanthridines; D002219:Carbamates / Q000494:pharmacology; D065607:Cytochrome P-450 Enzyme Inhibitors; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005231:Fatty Acids, Unsaturated / Q000494:pharmacology; D005682:Gadolinium / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D018482:Muscle, Skeletal / Q000098:blood supply*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000378:metabolism*; D009281:Naphthalenes / Q000494:pharmacology; D010617:Phenanthridines / Q000494:pharmacology; D048448:Phenylcarbamates; D010656:Phenylephrine / Q000494:pharmacology; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction; D019311:Staurosporine / Q000494:pharmacology; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors; D014661:Vasoconstriction / Q000187:drug effects