title: Role of endothelium-derived relaxing factors in arteriolar dilation during muscle contraction elicited by electrical field stimulation.
abstract: OBJECTIVE
  To determine the contribution of either endothelium-derived nitric oxide (EDNO) or prostaglandins in the functional vasodilation of first-order arterioles of the hamster cremaster muscle.
  
  
  METHODS
  First-order arterioles dilated from 72 +/- 3 microns to 93 +/- 4 microns in response to contraction of the cremaster muscle for 1 min (n = 7). After EDNO inhibition by topical application of 10 microM NW-nitro-L-arginine methyl ester (L-NAME), the resting diameter decreased to 66 +/- 3 microns and functional dilation was attenuated to 75 +/- 3 microns (P < 0.05). When the arteriolar diameter was returned to the control values by the addition of sodium nitroprusside, an NO donor, into the superfusion solution (n = 7), functional dilation was similar to that observed before EDNO inhibition (91 +/- 3 microns vs. 89 +/- 3 microns, P > 0.05). To evaluate whether the vasoconstrictor effect of L-NAME on functional dilation is same as other vasoconstrictors, norepinephrine was applied on the cremaster muscle to induce a vasoconstriction (72 +/- 2 to 66 +/- 1 micron, n = 7) equivalent to L-NAME.
  
  
  RESULTS
  Norepinephrine treatment attenuated functional dilation to 77 +/- 3 microns which was to a level similar to L-NAME treatment (P > 0.05). Inhibition of prostaglandin synthesis by topical application of indomethacin (28 microM) resulted in no significant changes in the resting diameter but functional vasodilation was attenuated from 89 +/- 2 to 81 +/- 3 microns (n = 7, P < 0.05).
  
  
  CONCLUSIONS
  These results suggest that EDNO is important for the resting tone of arterioles and that prostaglandins are important in modulating the functional dilation of the first-order arterioles in the hamster cremaster muscle.
authors.affiliation: Department of Physiology and Biophysics, University of Mississippi Medical Center, Jackson, MS 39216-4505, USA.
authors.forename: Y
authors.initials: Y
authors.lastname: Saito
authors.forename: A
authors.initials: A
authors.lastname: Eraslan
authors.forename: R L
authors.initials: RL
authors.lastname: Hester
mesh_terms: D000818:Animals; D001120:Arginine / Q000031:analogs & derivatives / Q000494:pharmacology; D001160:Arterioles / Q000187:drug effects / Q000502:physiology; D006224:Cricetinae; D004558:Electric Stimulation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007213:Indomethacin / Q000494:pharmacology; D009119:Muscle Contraction; D019331:NG-Nitroarginine Methyl Ester; D009569:Nitric Oxide / Q000502:physiology*; D009599:Nitroprusside / Q000494:pharmacology; D009638:Norepinephrine / Q000494:pharmacology; D011453:Prostaglandins / Q000096:biosynthesis; D014664:Vasodilation / Q000187:drug effects
chemical_list: D004791:Enzyme Inhibitors; D011453:Prostaglandins; D009599:Nitroprusside; D009569:Nitric Oxide; D001120:Arginine; D019331:NG-Nitroarginine Methyl Ester; D009638:Norepinephrine; D007213:Indomethacin