Pharmacodynamic Characterization of Nitric Oxide-Mediated Vasodilatory Activity in Isolated Perfused Rat Mesenteric Artery Bed

• Published in: Biological & Pharmaceutical Bulletin Vol. 34; no. 9; pp. 1487 - 1492
• Main Authors: Inoue, Shinsuke, Aiba, Tetsuya, Masaoka, Yasuyuki, Shimizu, Keiko, Komori, Yukiko, Mio, Mitsunobu, Takatori, Shingo, Kawasaki, Hiromu, Kurosaki, Yuji
• Format: Journal Article
• Language: English
• Published: Japan The Pharmaceutical Society of Japan 2011; Pharmaceutical Society of Japan; Japan Science and Technology Agency
• Subjects: acetylcholine; Acetylcholine - pharmacology; Animals; In Vitro Techniques; Male; Mesenteric Arteries - drug effects; Mesenteric Arteries - physiology; nitric oxide; Nitric Oxide - pharmacology; Nitric Oxide - physiology; Nitroprusside - pharmacology; pharmacodynamics; Rats; Rats, Wistar; sodium nitroprusside; vascular endothelium; vasodilation; Vasodilation - physiology
• ISSN: 0918-6158; 1347-5215
• DOI: 10.1248/bpb.34.1487

Vasodilation profiles following a short-term infusion of nitric oxide (NO), acetylcholine (ACh), and sodium nitroprusside (SNP) into an isolated perfused mesenteric artery bed were analyzed in rats to examine their vasodilatory efficacy under physiological conditions. These compounds commonly increase the intracellular NO concentration to exert vasodilatory activity. In an experiment with exogenous NO infusion where 100 μl of 1 : 300 diluted NO-saturated solution (approx. 53 pmol of NO) was applied, the infusion caused transient vasodilation in a dose-dependent manner, with the peak vasodilation value being 74.7% of the maximum relaxation value. In experiments with ACh, the peak vasodilation value was 81.5% of the maximum at a dose of 60 pmol. The vasodilation profile of ACh was similar to that of NO infusion, but the ACh-induced vasodilation reduced at a slower rate than that induced by NO infusion. The vasodilatory activity of SNP was less potent than that of ACh, and its peak value was 62.8% of the maximum at a dose of 2000 pmol. However, SNP activity was augmented by removing the vascular endothelia of the mesenteric artery bed, and the peak value reached 67.3% of the maximum at a dose of 60 pmol. Pharmacodynamic analysis indicated that NO and ACh are equivalent regarding their vasodilatory efficacy, while the efficacy of SNP was less than 1% of theirs, as the arterial vascular endothelium impeded intracellular SNP-related NO generation, by which 95% of SNP's vasodilatory efficacy was negated. These findings will be helpful to understand factors influencing the therapeutic efficacy of vasodilators.