Nitric oxide modulation of coronary artery myogenic tone in spontaneously hypertensive and Wistar-Kyoto rats.
1. The endothelium contributes substantially to the modulation of myogenic tone in coronary arteries from spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY). This study has addressed the contributions of endothelium-derived nitric oxide and cyclo-oxygenase products to this modulation in small coronary arteries (approximately 200 microns internal diameter) from 20-week-old SHR and WKY under pressurized, no-flow conditions in an arteriograph. 2. Active pressure-diameter relationships were uninfluenced by the cyclo-oxygenase inhibitor indomethacin (10 mumol/l) in either rat strain. In the presence of indomethacin and the nitric oxide synthase inhibitor N omega-nitro-L-arginine (L-NNA, 0.1 mmol/l), coronary arteries from SHR and WKY generated significantly greater myogenic tone. This increase in tone was similar in both strains. 3. In endothelium-denuded arteries, indomethacin and L-NNA did not influence tone. 4. Therefore, these results demonstrate that endothelium-derived nitric oxide is basally released to attenuate SHR and WKY coronary artery myogenic tone, whereas endothelium-derived cyclo-oxygenase products have no net vasoactive influence. Additionally, these data suggest that basal nitric oxide-mediated relaxation is normal in SHR coronary arteries and is therefore unlikely to be a pathogenic mechanism in this animal model of hypertension.
Garcia
S R
SR
University Department of Medicine, Manchester Royal Infirmary, U.K.
Bund
S J
SJ
D000818:Animals; D003331:Coronary Vessels / Q000503:physiopathology*; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology; D004730:Endothelium, Vascular / Q000503:physiopathology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006973:Hypertension / Q000503:physiopathology*; D007213:Indomethacin / Q000494:pharmacology; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000503:physiopathology; D009569:Nitric Oxide / Q000502:physiology*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D019335:Nitroarginine / Q000494:pharmacology; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D014661:Vasoconstriction / Q000187:drug effects; D014664:Vasodilation / Q000187:drug effects
D016861:Cyclooxygenase Inhibitors; D004791:Enzyme Inhibitors; D019335:Nitroarginine; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D007213:Indomethacin