title: Amplification effect and mechanism of action of ET-1 in U-46619-induced vasoconstriction in pig skin.
abstract: The aim of this study was to investigate if a low concentration of endothelin-1 (ET-1; 8 x 10(-10) M) may amplify the skin vasoconstrictor effect of other vasoactive substances in the pathogenesis of skin vasospasm. Pig skin flaps (6 x 16 cm) were perfused with Krebs buffer equilibrated with 95% O(2) and 5% CO(2) at 37 degrees 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 x 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 x 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 x 10(-10) M ET-1. Finally, the cyclooxygenase inhibitor indomethacin (5 x 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.
authors.affiliation: Research Institute, The Hospital for Sick Children, University of Toronto, Toronto, Ontario M5G 1X8. pang@sickkids.on.ca
authors.forename: C Y
authors.initials: CY
authors.lastname: Pang
authors.forename: H
authors.initials: H
authors.lastname: Xu
authors.forename: N
authors.initials: N
authors.lastname: Huang
authors.forename: C R
authors.initials: CR
authors.lastname: Forrest
authors.forename: T M
authors.initials: TM
authors.lastname: Perréault
authors.forename: P C
authors.initials: PC
authors.lastname: Neligan
mesh_terms: D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid / Q000494:pharmacology*; D000470:Alkaloids; D000818:Animals; D053119:Benzophenanthridines; D002118:Calcium / Q000494:pharmacology; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology; D004357:Drug Synergism; D019332:Endothelin-1 / Q000008:administration & dosage / Q000494:pharmacology*; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007213:Indomethacin / Q000494:pharmacology; D009638:Norepinephrine / Q000494:pharmacology; D010617:Phenanthridines / Q000494:pharmacology; D015240:Phorbol 12,13-Dibutyrate / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D012867:Skin / Q000098:blood supply*; D013552:Swine; D014661:Vasoconstriction / Q000187:drug effects*; D014662:Vasoconstrictor Agents / Q000494:pharmacology*
chemical_list: D000470:Alkaloids; D053119:Benzophenanthridines; D016861:Cyclooxygenase Inhibitors; D019332:Endothelin-1; D004791:Enzyme Inhibitors; D010617:Phenanthridines; D014662:Vasoconstrictor Agents; D015240:Phorbol 12,13-Dibutyrate; D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; C016299:chelerythrine; D011493:Protein Kinase C; D002118:Calcium; D009638:Norepinephrine; D007213:Indomethacin