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Contribution of Rho kinase to the early phase of the calcium–contraction coupling in airway smooth muscle
Author(s) -
Mbikou Prisca,
Fajmut Ales,
Brumen Milan,
Roux Etienne
Publication year - 2011
Publication title -
experimental physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.925
H-Index - 101
eISSN - 1469-445X
pISSN - 0958-0670
DOI - 10.1113/expphysiol.2010.054635
Subject(s) - myosin light chain phosphatase , contraction (grammar) , rho associated protein kinase , myosin light chain kinase , carbachol , dids , medicine , calcium , biophysics , endocrinology , muscle contraction , rho kinase inhibitor , myocyte , calmodulin , myosin , chemistry , stimulation , biology , kinase , biochemistry , membrane
We investigated theoretically and experimentally the role of Rho kinase (RhoK) in Ca 2+ –contraction coupling in rat airways. Isometric contraction was measured on tracheal, extrapulmonary and intrapulmonary bronchial rings. Intracellular [Ca 2+ ] was recorded in freshly isolated tracheal myocytes. Stimulation by carbachol (0.3 and 10 μ m ) and 50 m m external KCl induced a short‐time, Hill‐shaped contraction obtained within 90 s, followed by a sustained or an additional delayed contraction. Responses of [Ca 2+ ] i to acetylcholine consisted in a fast peak followed by a plateau and, in 42% of the cells, superimposed Ca 2+ oscillations. The RhoK inhibitor Y27632 (10 μ m ) did not alter the [Ca 2+ ] i response. Whatever the agonist, Y27632 did not modify the basal tension but decreased the amplitude of the short‐duration response, without altering the additional delayed contraction. The Myosin Light Chain Phosphatase (MLCP) inhibitor calyculin A increased the basal tension and abolished the effect of RhoK. KN93 (Ca 2+ –calmodulin‐dependent protein kinase II inhibitor) and DIDS (inhibitor of Ca 2+ ‐activated Cl − channels) had no influence on the RhoK effect. We built a theoretical model of Ca 2+ ‐dependent active/inactive RhoK ratio and subsequent RhoK‐dependent MLCP inactivation, which was further coupled with a four‐state model of the contractile apparatus and Ca 2+ ‐dependent MLCK activation. The model explains the time course of the short‐duration contraction and the role of RhoK by Ca 2+ ‐dependent activation of MLCK and RhoK, which inactivates MLCP. Oscillatory and non‐oscillatory [Ca 2+ ] i responses result in a non‐oscillatory contraction, the amplitude of which is encoded by the plateau value and oscillation frequency. In conclusion, Ca 2+ ‐dependent but CaMK II‐independent RhoK activation contributes to the early phase of the contractile response via MLCP inhibition.