Myosin light chain phosphorylation in human myometrial smooth muscle cells

L. W. MacKenzie, R. A. Word, M. L. Casey, J. T. Stull

Research output: Contribution to journalArticle

40 Scopus citations

Abstract

Ca2+/calmodulin-dependent phosphorylation of the 20-kDa regulatory light chain of myosin is of signal importance in the initiation of contraction in a number of smooth muscle tissues. In this investigation, we evaluated the relationship between intracellular free Ca2+ concentration ([Ca2+](i)) and the extent of myosin light chain phosphorylation in cultured human myometrial smooth muscle cells. Treatment of myometrial cells with ionomycin caused a concentration- and time-dependent increase in [Ca2+](i) and phosphorylation of myosin light chain. Temporally, the increases in light chain phosphorylation and [Ca2+](i) in response to ionomycin were similar. In myometrial cells treated with ionomycin (10-5 M) for 10 s, [Ca2+](i) increased from 138 to 800 nM; in these same cells, myosin light chain phosphorylation increased from 5% to a maximum value of 54%. Half-maximal phosphorylation of myosin light chain was attained at 300 nM [Ca2+](i). Treatment of myometrial smooth muscle cells with prostaglandin (PG) F(2α) (10-8 M) and PGE2 (10-8 M) caused a proportionate increase in [Ca2+](i) and myosin light chain phosphorylation. In addition, [Ca2+](i) and myosin light chain phosphorylation increased in response to oxytocin and angiotensin II. These findings indicate that a number of uterotonic agents effect an increase in [Ca2+](i), which in turn causes phosphorylation of myosin light chain. Furthermore, the concentration of Ca2+ in the cytoplasm is a primary determinant for myosin light chain phosphorylation in human myometrial smooth muscle cells.

Original languageEnglish (US)
Pages (from-to)C92-C98
JournalAmerican Journal of Physiology - Cell Physiology
Volume258
Issue number1 27-1
DOIs
StatePublished - Jan 1 1990

Keywords

  • angiotensin II
  • fura-2
  • ionomycin
  • oxytocin
  • prostaglandins

ASJC Scopus subject areas

  • Physiology
  • Cell Biology

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