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Smooth-muscle contraction without smooth-muscle myosin

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Creators Name:Morano, I. and Chai, G.X. and Baltas, L.G. and Lamounier-Zepter, V. and Lutsch, G. and Kott, M. and Haase, H. and Bader, M.
Journal Title:Nature Cell Biology
Journal Abbreviation:Nat Cell Biol
Page Range:371-375
Date:1 June 2000
Keywords:Blood Pressure, Body Weight, Cultured Cells, Fluorescent Antibody Technique, Intestines, Isoenzymes, Knockout Mice, Messenger RNA, Muscle Contraction, Mutation, Myosin Heavy Chains, Newborn Animals, Patent Ductus Arteriosus, Potassium Chloride, Protein Isoforms, Renin, Smooth Muscle, Urinary Bladder, Animals, Mice
Abstract:Here we have used gene-targeting to eliminate expression of smooth-muscle myosin heavy chain. Elimination of this gene does not affect expression of non-muscle myosin heavy chain, and knockout individuals typically survive for three days. Prolonged activation, by KCl depolarisation, of intact bladder preparations from wild-type neonatal mice produces an initial transient state (phase 1) of high force generation and maximal shortening velocity, which is followed by a sustained state (phase 2) characterized by low force generation and maximal shortening velocity. Similar preparations from knockout neonatal mice do not undergo phase 1, but exhibit a normal phase 2. We propose that, in neonatal smooth muscle phase 1 is generated by recruitment of smooth-muscle myosin heavy chain, whereas phase 2 can be generated by activation of non-muscle myosin heavy chain. We conclude that phase 1 becomes indispensable for survival and normal growth soon after birth, particularly for functions such as homeostasis and circulation.
Publisher:Nature Publishing Group (U.K.)
Item Type:Article

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