SKF-525A does not inhibit release of endothelium-derived relaxing factor from rat thoracic aorta and dog mesenteric and femoral artery.
SKF-525A (proadifen) inhibits endothelium-dependent relaxations induced by acetylcholine, arachidonic acid and the calcium ionophore A23187. This suggests that SKF-525A is an inhibitor of endothelium-derived relaxing factor (EDRF) and that EDRF may be a product of arachidonic acid metabolism formed via a cytochrome P-450-dependent pathway or that EDRF release is dependent on cytochrome P-450. We tested this postulate using both isolated rings of rat thoracic aorta and dog mesenteric and femoral artery and the perfusion-superfusion bioassay. Rings of rat thoracic aorta and dog mesenteric and femoral artery with intact endothelium were precontracted with an EC50 concentration of norepinephrine (0.1 nmol/l) or U46619 (0.05 mumol/l) and the relaxation to acetylcholine (ACh), bradykinin, adenosine triphosphate (ATP) or nitroglycerin (GTN) were obtained before, 30 min after addition of, and 30 min after washout of SKF-525A (50 mumol/l). SKF-525A inhibited ACh-induced endothelium-dependent relaxation of rat aortic rings and endothelium-dependent relaxation of the dog mesenteric and femoral artery produced by ACh and ATP, but did not affect relaxation to bradykinin or GTN. The inhibitory effect on SKF-525A on ACh and ATP-induced relaxation was partially reversed upon its washout from the muscle chamber. Pretreatment of the blood vessels with ibuprofen (1 mumol/l) did not attenuate SKF-525A-mediated inhibition of the relaxations to any agonist. Selective exposure of dog femoral artery (donor) to SKF-525A (50 mumol/l) for 60 min did not affect the relaxation responses of endothelium-rubbed coronary artery (bioassay tissue) to basal EDRF nor to the effluent from donor tissues stimulated with ACh (10-1,000 pmol), ATP (1-100 nmol) or bradykinin (3-100 pmol). The results show that SKF-525A exhibited a reversible inhibition of endothelium-dependent relaxation by a smooth muscle mechanism unrelated to the generation of EDRF from endothelium.
Xie
J M
JM
Department of Physiology, UMDNJ-New Jersey Medical School, Newark.
Wang
Y
Y
Greenberg
S S
SS
D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects / Q000378:metabolism*; D001681:Biological Assay; D004285:Dogs; D005260:Female; D005263:Femoral Artery / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D008638:Mesenteric Arteries / Q000187:drug effects / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism*; D009638:Norepinephrine / Q000494:pharmacology; D011335:Proadifen / Q000494:pharmacology*; D011450:Prostaglandin Endoperoxides, Synthetic / Q000494:pharmacology; D051381:Rats; D011921:Rats, Inbred WKY; D014661:Vasoconstriction / Q000187:drug effects
D011450:Prostaglandin Endoperoxides, Synthetic; D009569:Nitric Oxide; D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; D011335:Proadifen; D009638:Norepinephrine