PMID:10854329

Citation	Morano, I, Chai, GX, Baltas, LG, Lamounier-Zepter, V, Lutsch, G, Kott, M, Haase, H and Bader, M (2000) Smooth-muscle contraction without smooth-muscle myosin. Nat. Cell Biol. 2:371-5
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.
Links	PubMed Online version:10.1038/35014065
Keywords	Animals; Animals, Newborn; Blood Pressure/physiology; Body Weight; Cells, Cultured; Ductus Arteriosus, Patent/physiopathology; Female; Fluorescent Antibody Technique; Intestines/abnormalities; Intestines/physiology; Isoenzymes/deficiency; Isoenzymes/genetics; Isoenzymes/metabolism; Male; Mice; Mice, Knockout; Muscle Contraction/drug effects; Muscle Contraction/physiology; Muscle, Smooth/abnormalities; Muscle, Smooth/cytology; Muscle, Smooth/drug effects; Muscle, Smooth/physiology; Mutation/genetics; Myosin Heavy Chains/analysis; Myosin Heavy Chains/deficiency; Myosin Heavy Chains/genetics; Myosin Heavy Chains/physiology; Potassium Chloride/pharmacology; Protein Isoforms/analysis; Protein Isoforms/deficiency; Protein Isoforms/genetics; Protein Isoforms/physiology; RNA, Messenger/analysis; RNA, Messenger/genetics; Renin/blood; Urinary Bladder/abnormalities; Urinary Bladder/cytology; Urinary Bladder/drug effects; Urinary Bladder/physiology
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