Effect of NG-monomethyl-L-arginine on the beta-adrenoceptor-mediated relaxation of rat mesenteric resistance arteries.
beta-Adrenoceptors are present on vascular smooth muscle and on endothelium. We investigated whether the endothelial beta-adrenoceptors induce relaxation of rat mesenteric resistance arteries by stimulation of endothelium-derived relaxing factor (EDRF) release. To this end, the relaxation was studied in the presence and absence of 100 microM NG-monomethyl-L-arginine (L-NMMA), a specific inhibitor of the production of EDRF. The maximal relaxation with isoprenaline, expressed as a percentage of the precontraction, was 44.0 +/- 4.0% (n = 12) in the L-NMMA treated group and 58.0 +/- 2.6% (n = 13) in the untreated group, a statistically significant difference (P = 0.008). However, the precontraction with 40 mM K+ tended to be higher in the presence of L-NMMA. The pD2-value for isoprenaline was not significantly changed by the L-NMMA treatment. We conclude that the isoprenaline-mediated relaxation of mesenteric resistance arteries is inhibited by L-NMMA, but that this effect can at least in part be ascribed to an inhibition of baseline EDRF-release.
Dept. of Medicine, University Hospital Nijmegen, The Netherlands.
W M
WM
Blankesteijn
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Thien
D000818:Animals; D001120:Arginine / Q000031:analogs & derivatives* / Q000494:pharmacology; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D008638:Mesenteric Arteries / Q000187:drug effects*; D009126:Muscle Relaxation / Q000187:drug effects*; D009569:Nitric Oxide / Q000037:antagonists & inhibitors; D051381:Rats; D011921:Rats, Inbred WKY; D011943:Receptors, Adrenergic, beta / Q000187:drug effects*; D019323:omega-N-Methylarginine
D011943:Receptors, Adrenergic, beta; D019323:omega-N-Methylarginine; D009569:Nitric Oxide; D001120:Arginine; D007545:Isoproterenol