Different activation of the endothelial L-arginine and cyclooxygenase pathway in the human internal mammary artery and saphenous vein.
The endothelium releases substances controlling vascular tone and platelet function. We investigated mediators of endothelium-dependent responses in human internal mammary arteries and saphenous veins. The inhibitor of nitric oxide formation, NG-monomethyl L-arginine, enhanced the sensitivity to norepinephrine (fivefold) and evoked more pronounced endothelium-dependent contractions in internal mammary arteries (19 +/- 6% of 100 mM KCl) than in saphenous veins (2 +/- 1%; p less than 0.005). In internal mammary arteries, NG-monomethyl L-arginine, but not indomethacin, markedly reduced endothelium-dependent relaxations to acetylcholine (from 95 +/- 2% to 39 +/- 7%; p less than 0.005) and prevented those to histamine (78 +/- 6% to 4 +/- 3%; p less than 0.005). In saphenous veins, endothelium-dependent relaxations to acetylcholine were weak (24 +/- 11%), while nitric oxide caused comparable relaxations (85 +/- 3%) as in internal mammary arteries (80 +/- 5%; NS). NG-Monomethyl L-arginine prevented the relaxations to acetylcholine and unmasked endothelium-dependent contractions (30 +/- 10%). Indomethacin and the thromboxane synthetase inhibitor CGS-13080 augmented relaxations of saphenous veins to acetylcholine from 24 +/- 11% to 46 +/- 9% (p less than 0.05). Histamine-evoked contractions were converted to endothelium-dependent relaxations by indomethacin and the thromboxane A2/endoperoxide receptor antagonist SQ-30741 (38 +/- 3% and 40 +/- 6%; p less than 0.05) but not CGS-13080. Thus, 1) nitric oxide mediates endothelium-dependent relaxations in human arteries and veins; 2) internal mammary arteries release more nitric oxide than do saphenous veins, and 3) in saphenous veins, the effects of nitric oxide are reduced by endothelium-derived contracting factors originating from the cyclooxygenase pathway.
Yang
Z H
ZH
Department of Research, University Hospital, Basel, Switzerland.
von Segesser
L
L
Bauer
E
E
Stulz
P
P
Turina
M
M
Lüscher
T F
TF
D000109:Acetylcholine / Q000378:metabolism; D001120:Arginine / Q000378:metabolism*; D004730:Endothelium, Vascular / Q000378:metabolism*; D006636:Histamine Release; D006801:Humans; D008323:Mammary Arteries / Q000187:drug effects / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism / Q000494:pharmacology; D009638:Norepinephrine / Q000494:pharmacology; D011451:Prostaglandin-Endoperoxide Synthases / Q000378:metabolism*; D012501:Saphenous Vein / Q000187:drug effects / Q000378:metabolism*; D014661:Vasoconstriction; D014664:Vasodilation
D009569:Nitric Oxide; D001120:Arginine; D011451:Prostaglandin-Endoperoxide Synthases; D000109:Acetylcholine; D009638:Norepinephrine