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Vasoconstricting and vasodilating actions of halothane are unrelated to Ser19 MLC phosphorylation
Author(s) -
Lin Xue,
GarciaFerrer Josephine,
Boyle Walter A
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.5.a1178
Subject(s) - phosphorylation , dephosphorylation , halothane , chemistry , vasodilation , endocrinology , contraction (grammar) , medicine , phosphatase , biology , biochemistry , organic chemistry
Contraction or relaxation in smooth muscle is primarily dependent on Ser19 phosphorylation/dephosphorylation of the 20 kDa regulatory myosin light chain (MLC). In isolated mesenteric resistance blood vessels, halothane has a transient vasoconstricting action related to Ca2+release from ryanodine‐sensitive intracellular Ca2+ stores, and a long‐lasting vasodilating action. Whether these vasoconstricting and vasodilating actions of halothane depend on Ser19 phosphorylation/dephosphorylation of MLC has not been fully elucidated. Methods Vessels are cannulated and held at a constant transmural pressure (40mmHg) and image analysis is used to measure vessel diameter. Ser19 phosphorylation of MLC is quantified using the Western blotting technique and an Odyssey Infrared Imaging System. Results In physiologic saline solution (PSS), halothane (4.5 vol%) produced transient contraction to 51% of maximal and an increase in Ser 19 phosphorylation of MLC. Following a 30 min. incubation in PSS containing 0Ca2+ + 2mM EGTA, both halothane contraction and Ser19 phosphorylation were reduced. After incubation for 10 min in the kinase inhibitor wortmannin (10‐6M), halothane contraction was reduced but Ser19 phosphorylation was not affected. After a 15 min incubation with the phosphatase inhibitor calyculin A (3 X 10‐8M), halothane contraction was 52% of maximal with an increase in Ser19 phosphorylation, but a small contraction persisted in calyculin while MLC phosphorylation decreased below baseline. With halothane in PSS alone, the vessel diameter returned to baseline after approx. 20 sec, however the Ser19 phosphorylation decreased only a small amount. Conclusion The vasoconstricting and vasodilating actions of halothane appear to be poorly correlated with changes in MLC Ser19 phosphorylation levels.