Frequency-dependent myosin light chain phosphorylation in isolated myocardium

Paul J. Silver, L. Maximilian Buja, James T. Stull

Research output: Contribution to journalArticlepeer-review

36 Scopus citations


A specific light chain subunit (P-light chain) of myosin from striated and smooth muscles is phosphorylated by Ca2+•calmodulin-dependent myosin light chain kinase. Phosphorylation of cardiac P-light chain was examined in isolated perfused rabbit ventricular septae to determine the effect of contraction frequency on this Ca2+-dependent reaction. Muscles stimulated at 42 beats/min had 0.23 mol phosphate/mol P-light chain which decreased to 0.12 mol phosphate/mol P-light chain when the muscles were made quiescent (0 beats/min in the presence of 22 mm K+ for 30 min). Rephosphorylation of P-light chain to 0.24 mol phosphate/mol P-light chain occurred in muscles stimulated at 84 beats/min for 90 min but not in muscles stimulated at 42 beats/min for 30 min (0.15 mol phosphate/mol P-ligh chain). Stimulation at frequencies ranging from 0 to 126 beats/min for 30 min produced a frequency-dependent increase, in P-light chain phosphorylation from 0.1 to 0.4 mol phosphate/mol P-light chain. Increased inotropy for 30 s with isoproterenol was not associated with significant increases in phorylation and dephosphorylation in ventricular muscle are much slower than the reported rates of phosphorylation in either fast-twitch skeletal or smooth muscles. The extent of cardiac P-light chain phosphorylation appears dependent upon the steady-state frequency of contraction.

Original languageEnglish (US)
Pages (from-to)31-37
Number of pages7
JournalJournal of Molecular and Cellular Cardiology
Issue number1
StatePublished - Jan 1986


  • Myosin phosphorylation
  • Positive inotropy
  • Stimulus frequency

ASJC Scopus subject areas

  • Molecular Biology
  • Cardiology and Cardiovascular Medicine


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