Nitric oxide-dependent opposite effects of somatostatin on arterial and venous caliber in situ.
The vascular effects of somatostatin (ST) and its mechanism of action are not well understood. In the present study, we investigated the direct effects of ST on the vascular tone of rat saphenous artery and vein using videomicroangiometry in situ. ST was administered either in superfusion or in infusion. We found opposite effects in arteries and veins: ST (10(-12)-10(-7) M) dilated the artery (outer diameter increased from 533 +/- 28 to 600 +/- 29 microns, administered in superfusion) and contracted the vein (from 709 +/- 26 to 640 +/- 26 microns and from 775 +/- 30 to 708 +/- 60 microns in superfusion and infusion, respectively). These effects of ST were completely abolished after deendothelization (air bolus maintained for 6 min in vessel lumen) and after local infusion of NG-nitro-L-arginine (L-NNA; 10(-4) M), a nitric oxide (NO) synthesis inhibitor. An NO-dependent basal vasodilator tone in the rat saphenous vein responsible for 10.9 +/- 0.3% of the total vessel diameter was found. After ST administration the venous diameter reduction was similar to that measured after deendothelization or L-NNA. We conclude that ST in situ induces NO release from endothelial cells of rat saphenous artery causing vasodilation, whereas, in contrast, it inhibits the basal NO-dependent vasodilator tone of the saphenous vein inducing vasoconstriction.
Szentiványi
M
M
Clinical Research Department-Second Institute of Physiology, Semmelweis University of Medicine, Budapest, Hungary.
Nádasy
G L
GL
Dézsi
L
L
Mózes
G
G
Tulassay
T
T
Monos
E
E
D000818:Animals; D001158:Arteries / Q000187:drug effects; D004730:Endothelium, Vascular / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D008297:Male; D009569:Nitric Oxide / Q000037:antagonists & inhibitors / Q000502:physiology*; D019335:Nitroarginine / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012501:Saphenous Vein / Q000187:drug effects*; D013004:Somatostatin / Q000494:pharmacology*; D013848:Thigh / Q000098:blood supply*; D014661:Vasoconstriction; D014664:Vasodilation
D004791:Enzyme Inhibitors; D019335:Nitroarginine; D009569:Nitric Oxide; D013004:Somatostatin