Amplification effect and mechanism of action of ET-1 in U-46619-induced vasoconstriction in pig skin

• Published in: American journal of physiology. Regulatory, integrative and comparative physiology integrative and comparative physiology, 2001-03, Vol.280 (3), p.713-R720
• Main Authors: Pang, Cho Y, Xu, Huai, Huang, Ning, Forrest, Christopher R, Perreault, Therese M, Neligan, Peter C
• Format: Article
• Language: English
• Subjects: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid - pharmacology; Alkaloids; Animals; Benzophenanthridines; Calcium - pharmacology; Cyclooxygenase Inhibitors - pharmacology; Drug Synergism; Endothelin-1 - administration & dosage; Endothelin-1 - pharmacology; Enzyme Activation - drug effects; Enzyme Inhibitors - pharmacology; Indomethacin - pharmacology; Norepinephrine - pharmacology; Phenanthridines - pharmacology; Phorbol 12,13-Dibutyrate - pharmacology; Protein Kinase C - antagonists & inhibitors; Protein Kinase C - metabolism; Skin - blood supply; Swine; Vasoconstriction - drug effects; Vasoconstrictor Agents - pharmacology
• ISSN: 0363-6119; 1522-1490
• DOI: 10.1152/ajpregu.2001.280.3.r713

1  Research Institute, The Hospital for Sick Children, and Departments of 2  Surgery and 3  Physiology, University of Toronto, Toronto, Ontario M5G 1X8, and 4  Division of Newborn Medicine, The Montreal Children's Hospital, Montreal, Quebec H3H 1P3, Canada The aim of this study was to investigate if a low concentration of endothelin-1 (ET-1; 8 × 10 10 M) may amplify the skin vasoconstrictor effect of other vasoactive substances in the pathogenesis of skin vasospasm. Pig skin flaps (6 × 16 cm) were perfused with Krebs buffer equilibrated with 95% O 2 and 5% CO 2 at 37°C and pH 7.4. Skin perfusion pressure measured by a pressure transducer and skin perfusion assessed by the dermofluorometry technique were used for assessment of skin vasoconstriction. We observed that ET-1 (8 × 10 10 M) significantly amplified the concentration-dependent (10 7 -10 5 M) skin vasoconstrictor effect of norepinephrine. More importantly, we observed for the first time that this low concentration of ET-1 also amplified the concentration-dependent (10 8 -10 6 M) skin vasoconstrictor effect of the thromboxane A 2 mimetic U-46619, and this amplification effect of ET-1 was completely blocked by the protein kinase C (PKC) inhibitor chelerythrine (5 × 10 6 M). Conversely, the PKC activator phorbol 12,13-dibutyrate (10 7 M) amplified the vasoconstrictor effect of U-46619. Furthermore, the sensitivity of the skin vasculature to the vasoconstrictor effect of extracellular Ca 2+ in U-46619-induced skin vasoconstriction was significantly enhanced in the presence of 8 × 10 10 M ET-1. Finally, the cyclooxygenase inhibitor indomethacin (5   × 10 6 M) did not affect the amplification effect of ET-1 on U-46619-induced skin vasoconstriction. We conclude that a low concentration of ET-1 can amplify the skin vasoconstrictor effect of U-46619 independent of endogenous cyclooxygenase products, and the mechanism may involve activation of PKC and increase in sensitivity of the contractile apparatus to Ca 2+ in smooth muscle cells. skin vasospasm; endothelin-1; protein kinase C; Ca 2+ sensitivity