Biochemical markers of contraction in human myometrial smooth muscle cells in culture |
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Authors: | Marilyn R Richardson Doris A Taylor M Linette Casey Paul C Macdonald James T Stull |
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Institution: | (1) Cecil H. and Ida Green Center for Reproductive Biology Sciences, The University of Texas, Health Science Center at Dallas, 75235 Dallas, Texas;(2) Department of Biochemistry, The University of Texas, Health Science Center at Dallas, 75235 Dallas, Texas;(3) Department of Obstetrics and Gynecology, The University of Texas, Health Science Center at Dallas, 75235 Dallas, Texas;(4) Department of Pharmacology, The University of Texas, Health Science Center at Dallas, 75235 Dallas, Texas;(5) Department of Physiology, University of Texas Health Science Center at Dallas, 5323 Harry Hines Boulevard, 75235 Dallas, Texas |
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Abstract: | Summary Phosphorylation of a light chain subunit of myosin by Ca2+ and calmodulin-dependent myosin light chain kinase is believed to be essential for smooth muscle contraction. The biochemical
properties of the myosin phosphorylation system in human myometrial smooth muscle cells in monolayer culture were compared
with those of human myometrial tissue and nonmuscle cells in culture. Native myosin was isolated from other cellular proteins
of crude homogenates by polyacrylamide gel electrophoresis (in the presence of pyrophosphate) and quantified by densitometry.
The myosin content of myometrial smooth muscle cells in culture and that of myometrial tissue were similar and four- to five-fold
greater than that of human endometrial stromal cells or skin fibroblasts in culture. The specific activities of myosin light
chain kinase in homogenates of myometrial smooth muscle cells that were maintained in culture and in myometrial tissue were
similar (2.05±0.18 and 1.60±0.37 nmol phosphate incorporated per min per mg protein, respectively). On the other hand, enzyme
activity in skin fibroblasts was only 5% of that in myometrial smooth muscle cells. Myosin light chain kinase activity in
myometrial smooth muscle cells was dependent upon Ca2+ and was inhibited reversibly by the calmodulin antagonist, calmidazolium. The intracellular Ca2+ concentration measured by quin2 fluorescence was 0.12 μM in resting cells and increased in a concentration-dependent manner with KC1 to a maximal value of 0.47 μM. These results indicate that biochemical processes important for smooth muscle contraction are retained in human myometrial
smooth muscle cells in culture.
This research was supported by grants HL26043, HD11149, and GM07062 from the National Institutes of Health, Bethesda, MD. |
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Keywords: | calcium myosin phosphorylation calmodulin myometrial smooth muscle cells |
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