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Decreased phosphatase activity, increased Ca2+ sensitivity, and myosin light chain phosphorylation in urinary bladder smooth muscle of newborn mice

Ekman, Mari LU ; Fagher, K; Wede, Mia LU ; Stakeberg, K and Arner, Anders LU (2005) In Journal of General Physiology 125(2). p.187-196
Abstract
Developmental changes in the regulation of smooth muscle contraction were examined in urinary bladder smooth muscle from mice. Maximal active stress was lower in newborn tissue compared with adult, and it was correlated with a lower content of actin and myosin. Sensitivity to extracellular Ca2+ during high-K+ contraction, was higher in newborn compared with 3-wk-old and adult bladder strips. Concentrations at half maximal tension (EC50) were 0.57 +/- 0.01, 1.14 +/- 0.12, and 1.31 +/- 0.08 mM. Force of the newborn tissue was inhibited by similar to45% by the nonmuscle myosin inhibitor Blebbistatin, whereas adult tissue was not affected. The calcium sensitivity in newborn tissue was not affected by Blebbistatin, suggesting that noninuscle... (More)
Developmental changes in the regulation of smooth muscle contraction were examined in urinary bladder smooth muscle from mice. Maximal active stress was lower in newborn tissue compared with adult, and it was correlated with a lower content of actin and myosin. Sensitivity to extracellular Ca2+ during high-K+ contraction, was higher in newborn compared with 3-wk-old and adult bladder strips. Concentrations at half maximal tension (EC50) were 0.57 +/- 0.01, 1.14 +/- 0.12, and 1.31 +/- 0.08 mM. Force of the newborn tissue was inhibited by similar to45% by the nonmuscle myosin inhibitor Blebbistatin, whereas adult tissue was not affected. The calcium sensitivity in newborn tissue was not affected by Blebbistatin, suggesting that noninuscle myosin is not a primary cause for increased calcium sensitivity. The relation between intracellular [Ca2+] and force was shifted toward lower [Ca2+] in the newborn bladders. This increased Ca2+ sensitivity was also found in permeabilized muscles (EC50: 6.10 +/- 0.07, 5.77 +/- 0.08, and 5.55 +/- 0.02 pCa units, in newborn, 3-wk-old, and adult tissues). It was associated with an increased myosin light chain phosphorylation and a decreased rate of dephosphorylation. No difference was observed in the myosin light chain phosphorylation rate, whereas the rate of myosin light chain phosphatase-induced relaxation was about twofold slower in the newborn tissue. The decreased rate was associated with a lower expression of the phosphatase regulatory Subunit MYPT-1 in newborn tissue. The results show that myosin light chain phosphatase activity can be developmentally regulated in mammalian urinary bladders. The resultant alterations in Ca2+ sensitivity may be of importance for the nervous and myogenic control of the newborn bladders. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Journal of General Physiology
volume
125
issue
2
pages
187 - 196
publisher
Rockefeller Institute for Medical Research
external identifiers
  • wos:000227089700008
  • pmid:15684094
  • scopus:13544256608
ISSN
0022-1295
DOI
10.1085/jgp.200409212
language
English
LU publication?
yes
id
d95825b1-ab53-4932-8752-aab7cabb73d1 (old id 253590)
date added to LUP
2007-08-08 14:34:21
date last changed
2017-08-13 04:28:59
@article{d95825b1-ab53-4932-8752-aab7cabb73d1,
  abstract     = {Developmental changes in the regulation of smooth muscle contraction were examined in urinary bladder smooth muscle from mice. Maximal active stress was lower in newborn tissue compared with adult, and it was correlated with a lower content of actin and myosin. Sensitivity to extracellular Ca2+ during high-K+ contraction, was higher in newborn compared with 3-wk-old and adult bladder strips. Concentrations at half maximal tension (EC50) were 0.57 +/- 0.01, 1.14 +/- 0.12, and 1.31 +/- 0.08 mM. Force of the newborn tissue was inhibited by similar to45% by the nonmuscle myosin inhibitor Blebbistatin, whereas adult tissue was not affected. The calcium sensitivity in newborn tissue was not affected by Blebbistatin, suggesting that noninuscle myosin is not a primary cause for increased calcium sensitivity. The relation between intracellular [Ca2+] and force was shifted toward lower [Ca2+] in the newborn bladders. This increased Ca2+ sensitivity was also found in permeabilized muscles (EC50: 6.10 +/- 0.07, 5.77 +/- 0.08, and 5.55 +/- 0.02 pCa units, in newborn, 3-wk-old, and adult tissues). It was associated with an increased myosin light chain phosphorylation and a decreased rate of dephosphorylation. No difference was observed in the myosin light chain phosphorylation rate, whereas the rate of myosin light chain phosphatase-induced relaxation was about twofold slower in the newborn tissue. The decreased rate was associated with a lower expression of the phosphatase regulatory Subunit MYPT-1 in newborn tissue. The results show that myosin light chain phosphatase activity can be developmentally regulated in mammalian urinary bladders. The resultant alterations in Ca2+ sensitivity may be of importance for the nervous and myogenic control of the newborn bladders.},
  author       = {Ekman, Mari and Fagher, K and Wede, Mia and Stakeberg, K and Arner, Anders},
  issn         = {0022-1295},
  language     = {eng},
  number       = {2},
  pages        = {187--196},
  publisher    = {Rockefeller Institute for Medical Research},
  series       = {Journal of General Physiology},
  title        = {Decreased phosphatase activity, increased Ca2+ sensitivity, and myosin light chain phosphorylation in urinary bladder smooth muscle of newborn mice},
  url          = {http://dx.doi.org/10.1085/jgp.200409212},
  volume       = {125},
  year         = {2005},
}