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Regional variation in myosin isoforms and phosphorylation at the resting tone in urinary bladder smooth muscle

Regional variation in myosin isoforms and phosphorylation at the resting tone in urinary bladder... Abstract Urinary bladder filling and emptying requires coordinated control of bladder body and urethral smooth muscles. Bladder dome, midbladder, base, and urethra showed significant differences in the percentage of 20-kDa myosin light chain (LC 20 ) phosphorylation (35.45 ± 4.6, 24.7 ± 2.2, 13.6± 2.1, and 12.8 ± 2.7%, respectively) in resting muscle. Agonist-mediated force was associated with a rise in LC 20 phosphorylation, but the extent of phosphorylation at all levels of force was less for urethral than for bladder body smooth muscle. RT-PCR and quantitative competitive RT-PCR analyses of total RNA from bladder body and urethral smooth muscles revealed only a slight difference in myosin heavy chain mRNA copy number per total RNA, whereas mRNA copy numbers for NH 2 -terminal isoforms SM-B (inserted) and SM-A (noninserted) in these muscles showed a significant difference (2.28 × 10 8 vs. 1.68 × 10 8 for SM-B and 0.12 × 10 8 vs. 0.42 × 10 8 for SM-A, respectively), which was also evident at the protein level. The ratio of COOH-terminal isoforms SM2:SM1 in the urethra was moderately but significantly lower than that in other regions of the bladder body. A high degree of LC 20 phosphorylation and SM-B in the bladder body may help to facilitate fast cross-bridge cycling and force generation required for rapid emptying, whereas a lower level of LC 20 phosphorylation and the presence of a higher amount of SM-A in urethral smooth muscle may help to maintain the high basal tone of urethra, required for urinary continence. myosin isoform urethra urinary continence Footnotes Address for reprint requests and other correspondence: S. Chacko, Dept. of Pathobiology and Division of Urology, Univ. of Pennsylvania, 3800 Spruce St., Philadelphia, PA 19104 (E-mail: chackosk@mail.med.upenn.edu ). The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “ advertisement ” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. Copyright © 2001 the American Physiological Society http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png AJP - Cell Physiology The American Physiological Society

Regional variation in myosin isoforms and phosphorylation at the resting tone in urinary bladder smooth muscle

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Publisher
The American Physiological Society
Copyright
Copyright © 2010 the American Physiological Society
ISSN
0363-6143
eISSN
1522-1563
Publisher site
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Abstract

Abstract Urinary bladder filling and emptying requires coordinated control of bladder body and urethral smooth muscles. Bladder dome, midbladder, base, and urethra showed significant differences in the percentage of 20-kDa myosin light chain (LC 20 ) phosphorylation (35.45 ± 4.6, 24.7 ± 2.2, 13.6± 2.1, and 12.8 ± 2.7%, respectively) in resting muscle. Agonist-mediated force was associated with a rise in LC 20 phosphorylation, but the extent of phosphorylation at all levels of force was less for urethral than for bladder body smooth muscle. RT-PCR and quantitative competitive RT-PCR analyses of total RNA from bladder body and urethral smooth muscles revealed only a slight difference in myosin heavy chain mRNA copy number per total RNA, whereas mRNA copy numbers for NH 2 -terminal isoforms SM-B (inserted) and SM-A (noninserted) in these muscles showed a significant difference (2.28 × 10 8 vs. 1.68 × 10 8 for SM-B and 0.12 × 10 8 vs. 0.42 × 10 8 for SM-A, respectively), which was also evident at the protein level. The ratio of COOH-terminal isoforms SM2:SM1 in the urethra was moderately but significantly lower than that in other regions of the bladder body. A high degree of LC 20 phosphorylation and SM-B in the bladder body may help to facilitate fast cross-bridge cycling and force generation required for rapid emptying, whereas a lower level of LC 20 phosphorylation and the presence of a higher amount of SM-A in urethral smooth muscle may help to maintain the high basal tone of urethra, required for urinary continence. myosin isoform urethra urinary continence Footnotes Address for reprint requests and other correspondence: S. Chacko, Dept. of Pathobiology and Division of Urology, Univ. of Pennsylvania, 3800 Spruce St., Philadelphia, PA 19104 (E-mail: chackosk@mail.med.upenn.edu ). The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “ advertisement ” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. Copyright © 2001 the American Physiological Society

Journal

AJP - Cell PhysiologyThe American Physiological Society

Published: Feb 1, 2001

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