Acetylcholine- and flow-induced production and release of nitric oxide in arterial and venous endothelial cells.
To study flow-mediated responses in a conduit vein, we investigated the physiological characteristics of endothelium-dependent acetylcholine (ACh)- and flow-induced relaxations using a conventional bioassay cascade. Cylindrical segments isolated from canine common carotid arteries and external jugular veins were perfused at a constant mean flow rate ranging from 1 to 8 ml/min. Endothelium-derived nitric oxide (NO) activity in perfusion effluent through the arterial and venous segments was measured by relaxation of endothelium-denuded arterial rings and arterial and/or venous rings precontracted by prostaglandin F2 alpha, respectively. Stimulation by a flow rate of 8 ml/min on the arterial and venous endothelial cells produced approximately 60 and 20% of the maximum relaxation in the arterial and venous rings, respectively. ACh (10(-6) and 10(-5) M) perfused through the arterial and venous segments with endothelium caused dose-related relaxations of both bioassay rings. The ACh- and flow-induced relaxations were completely reduced by mechanical removal of the endothelial cells. Pretreatment with 5 x 10(-5) M NG-nitro-L-arginine methyl ester (L-NAME) produced a significant reduction of the ACh- and flow-induced vasodilation. Additional treatment with 10(-4) M L-arginine significantly reversed the L-NAME-induced inhibition of ACh-induced relaxation but had no effect on flow-induced relaxation. When the flow rate was increased from 2 to 4 ml/min, the same concentrations of ACh produced larger dose-related relaxations than those obtained at a flow rate of 2 ml/min. Pretreatment with 25 U/ml superoxide dismutase caused no significant effect on the flow-mediated potentiation of ACh-induced relaxation. These findings suggest that venous endothelial cells of canine large vein are able to produce and release NO by stimulation of increased flow or ACh to a significantly lesser extent compared with the artery and that ACh-induced vasodilation is potentiated by an increase in shear stress up to approximately 4 dyn/cm2 loaded on the endothelial cells.
Fukaya
Y
Y
First Department of Physiology; Shinshu University School of Medicine, Matsumoto, Japan.
Ohhashi
T
T
D000109:Acetylcholine / Q000494:pharmacology*; D000818:Animals; D001120:Arginine / Q000494:pharmacology; D001158:Arteries / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D001775:Blood Circulation / Q000502:physiology*; D004285:Dogs; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D005260:Female; D008297:Male; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D013314:Stress, Mechanical; D014664:Vasodilation / Q000187:drug effects / Q000502:physiology; D014680:Veins / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*
D009569:Nitric Oxide; D001120:Arginine; D019001:Nitric Oxide Synthase; D000109:Acetylcholine; D019331:NG-Nitroarginine Methyl Ester