Arteriolar dilation produced by venule endothelium-derived nitric oxide.
OBJECTIVE
We conducted bioassay experiments to determine whether nitric oxide produced by endothelial cells (endothelial-derived nitric oxide, or EDNO) within large venules could act to dilate arterioles.


METHODS
In these experiments parallel segments of first-order arterioles and venules were isolated from skeletal muscle and were cannulated in series with a glass connecting tube (length: 300-500 microns). Arterioles were mechanically denuded of endothelium by a delicate yet abrasive rubbing technique. Venular endothelium remained intact. Endothelial denudation of arterioles was confirmed by the absence of dilation during exposure to acetylcholine (10(-6) mol/L). The cannulated vessels were pressurized to 30 cm H2O and the arterioles pre-constricted by approximately 50% with norepinephrine (10(-10) mol/L).


RESULTS
Topical applications of acetylcholine (10(-6) mol/L) or bradykinin (10(-9) mol/L) during luminal perfusion from venule to arteriole produced significant arteriolar dilation. In contrast, a slight arteriolar constriction was observed when the direction of flow was reversed (i.e., arteriole to venule) in the presence of either acetylcholine (10(-6) mol/L) or bradykinin (10(-9) mol/L). Inhibition of venular EDNO with NG-monomethyl-L-arginine (L-NMMA; 10(-5) mol/L; 1 hour) completely abolished the arteriolar dilation observed in response to acetylcholine or bradykinin during venule to arteriole perfusion.


CONCLUSIONS
These results demonstrate that venular-derived EDNO can relax arteriolar vascular smooth muscle.
Falcone
J C
JC
Department of Physiology and Biophysics, School of Medicine, University of Louisville, KY 40292, USA.
Meininger
G A
GA
D000241:Adenosine / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D001160:Arterioles / Q000187:drug effects* / Q000502:physiology*; D004730:Endothelium, Vascular / Q000502:physiology*; D008297:Male; D008833:Microcirculation / Q000187:drug effects / Q000502:physiology; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology; D009569:Nitric Oxide / Q000378:metabolism / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012039:Regional Blood Flow / Q000187:drug effects; D014664:Vasodilation / Q000187:drug effects; D014699:Venules / Q000502:physiology*
D009569:Nitric Oxide; D000241:Adenosine