Role of Ca2+ and myosin light chain phosphorylation in regulation of smooth muscle.

M. O. Aksoy, R. A. Murphy, K. E. Kamm

Research output: Contribution to journalArticle

Abstract

The time course of phosphorylation of the 20,000-dalton myosin light chain (LC 20) was determined during contraction and relaxation in K+- and histamine-stimulated medial strips of swine carotid arteries. Resting LC 20 phosphorylation levels of 0.15 mol P/mol LC 20 rapidly increased to peak values of 0.6-0.7 mol P/mol LC 20 after stimulation and then declined significantly, although stress continued to rise to a stable steady-state maximum. LC 20 dephosphorylation after agonist washout preceded the decline in isometric stress. Over the entire contraction-relaxation cycle, phosphorylation was correlated with shortening velocity and not with developed stress. The maximum shortening velocity with no external load (Vo) was directly proportional to LC 20 phosphorylation (r = 0.986). The data indicate that LC 20 phosphorylation is necessary for cross-bridge cycling leading to shortening or stress development but that stress can be maintained by additional mechanisms. We suggest that dephosphorylation of an attached cross bridge in the presence of Ca2+ arrests the cycle, forming an attached, noncycling cross bridge.

Original languageEnglish (US)
JournalThe American journal of physiology
Volume242
Issue number1
StatePublished - Jan 1982

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Myosin Light Chains
Smooth Muscle
Phosphorylation
Carotid Arteries
Histamine
Swine

ASJC Scopus subject areas

  • Medicine(all)

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Role of Ca2+ and myosin light chain phosphorylation in regulation of smooth muscle. / Aksoy, M. O.; Murphy, R. A.; Kamm, K. E.

In: The American journal of physiology, Vol. 242, No. 1, 01.1982.

Research output: Contribution to journalArticle

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