Decreased Phosphatase Activity, Increased Ca2+ Sensitivity, and Myosin Light Chain Phosphorylation in Urinary Bladder Smooth Muscle of Newborn Mice

Ekman, Mari; Fagher, Katarina; Wede, Mia; Stakeberg, Karolina; Arner, Anders

doi:10.1085/jgp.200409212

Cited by 30 publications

(51 citation statements)

References 27 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Consistent with previous studies with different neonatal SMs (8,9,11,12,14,31), we found that actin and myosin expression and specific active peak force elicited by KCl and carbachol at optimal length were lower compared with the adult. Specific force takes into account that the mechanical output depends on multiple factors, some of which are difficult to assess.…”

Section: Excitation Contraction Coupling In Relation To Contractile Psupporting

confidence: 92%

Neonatal mouse ileum: functional properties and protein composition of the contractile machinery

et al. 2014

View full text Add to dashboard Cite

Background: Immature motility of the ileum may contribute to life-threatening diseases. Little is known about the normal biomechanics of the neonatal ileum in relation to the protein composition of its contractile machinery. Methods: We analyzed the tissue architecture, the biomechanics in intact and β-escin-permeabilized preparations, and the protein composition in neonatal (P0) and adult murine ileum. results: Muscle thickness of the P0 ileum was −50% of the adult ileum and passive compliance was higher. Carbachol-and KCl-elicited contractions were tonic rather than phasic as in the adult. Ca 2+ sensitivity was higher and relaxation rate was slower in β-escin-permeabilized P0 compared with adult ileum. The expression level of β-actin relative to α-actin was higher, and those of total actin, myosin, myosin light chain kinase, the catalytic subunit of myosin phosphatase and telokin were lower compared with the adult. The expression level of MYPT1 was similar, but P0 ileum expressed only the M133; the adult ileum also expressed the M130 isoform. conclusion: The mechanical features and protein composition of the P0 ileum are similar to those of adult tonic smooth muscles. We propose that this is highly adaptive during fetal life allowing the small intestine to act predominantly as a container. d uring development from fetal to newborn and adult life, the gastrointestinal tract (GIT) gradually establishes its mature structure and function. Anatomic features of the digestive tract are present already in human fetal life by 8 wk gestational age (1). However, gastrointestinal motility of preterm individuals is reduced (2). Obviously, this poses severe problems regarding oral food intake which are aggravated by the fact that the immaturity of the GIT, singly or in concert with other perinatal risk factors, may contribute to complications such as spontaneous intestinal perforation, not uncommon in extremely low-birth-weight infants (3). The underlying cause of spontaneous intestinal perforation, one of the leading risk factors of death in neonatal medicine, is still poorly understood. Conceivably an immature intestinal motility is an important determinant leading to stasis of the intestinal contents and overgrowth of infectious enteritis pathogens (4). The ensuing inflammatory response leads to a viscous cycle by not only further impairing of propulsive gut movements but also derogating vascular smooth muscle (SM) function, leading to reduced blood supply and finally to necrosis.Intestinal motility is driven by the concerted action of enteric neurons, pacemaker, and SM cells (2). Although several studies addressed different aspects of the fetal and postnatal maturation of innervation, electrical activity, and global contractile activity of the GIT (5-7), only few studies addressed in some depth the properties of the downstream effector, the SM. Investigations from avian (8) and mammalian stomach (9-11), and guinea pig gallbladder (12) as well as from non-GIT organs like urinary bladder (13,14), revealed major difference...

show abstract

Section: Excitation Contraction Coupling In Relation To Contractile Psupporting

confidence: 92%

Neonatal mouse ileum: functional properties and protein composition of the contractile machinery

et al. 2014

View full text Add to dashboard Cite

show abstract

“…In support of this hypothesis, contractions produced by bladder from newborn mice that express predominantly nonmuscle myosin II, but not adult mice that express predominantly smooth muscle myosin II, are inhibited by 10 M (Ϫ)blebbistatin (Ekman et al, 2005). In contrast, Rhee et al (2006) recently showed that tonic contractions of adult mouse aorta and bladder are inhibited by (Ϫ)blebbistatin, and based on data suggesting that blebbistatin is selective for inhibition of nonmuscle over smooth muscle myosin II (Limouze et al, 2004), these authors concluded that tonic contractions are dependent on nonmuscle myosin.…”

Section: Discussionmentioning

confidence: 87%

“…Tonic force maintenance has been attributed to nonmuscle myosin II (Morano, 2003;Limouze et al, 2004;Ekman et al, 2005). We therefore examined the relative expression of smooth and nonmuscle myosin II in rabbit renal, femoral, and saphenous arteries and chicken carotid artery and gizzard.…”

Section: Blebbistatin Inhibits Arterial Contraction and Myosin Atpasementioning

confidence: 99%

Potent Inhibition of Arterial Smooth Muscle Tonic Contractions by the Selective Myosin II Inhibitor, Blebbistatin

Eddinger¹,

Meer²,

Miner³

et al. 2006

J Pharmacol Exp Ther

View full text Add to dashboard Cite

Blebbistatin is reported to be a selective and specific small molecule inhibitor of the myosin II isoforms expressed by striated muscles and nonmuscle (IC 50 ϭ 0.5-5 M) but is a poor inhibitor of purified turkey smooth muscle myosin II (IC 50 ϳ80 M). We found that blebbistatin potently (IC 50 ϳ3 M) inhibited the actomyosin ATPase activities of expressed "slow" [smooth muscle myosin IIA (SMA)] and "fast" [smooth muscle myosin IIB (SMB)] smooth muscle myosin II heavy-chain isoforms. Blebbistatin also inhibited the KCl-induced tonic contractions produced by rabbit femoral and renal arteries that express primarily SMA and the weaker tonic contraction produced by the saphenous artery that expresses primarily SMB, with an equivalent potency comparable with that identified for nonmuscle myosin IIA (IC 50 ϳ5 M). In femoral and saphenous arteries, blebbistatin had no effect on unloaded shortening velocity or the tonic increase in myosin light-chain phosphorylation produced by KCl but potently inhibited ␤-escin permeabilized artery contracted with calcium at pCa 5, suggesting that cell signaling events upstream from KCl-induced activation of cross-bridges were unaffected by blebbistatin. It is noteworthy that KCl-induced contractions of chicken gizzard were less potently inhibited (IC 50 ϳ20 M). Adult femoral, renal, and saphenous arteries did not express significant levels of nonmuscle myosin. These data together indicate that blebbistatin is a potent inhibitor of smooth muscle myosin II, supporting the hypothesis that the force-bearing structure responsible for tonic force maintenance in adult mammalian vascular smooth muscle is the cross-bridge formed from the blebbistatin-dependent interaction between actin and smooth muscle myosin II.

show abstract

“…In the present study we documented that the fetal and newborn pulmonary arterial tissue has a lower MYPT content when compared with the adult. The rate of MLCP-induced relaxation has been shown to be dependent on the MYPT content and is lowest in the newborn mice bladder smooth muscle (13), suggesting that a similar mechanism may be operative in the pulmonary vascular tissue.…”

Section: Discussionmentioning

confidence: 99%

Rat pulmonary arterial smooth muscle myosin light chain kinase and phosphatase activities decrease with age

Belik

Kerc

Pato

2006

American Journal of Physiology-Lung Cellular and Molecular Phys

View full text Add to dashboard Cite

Belik, J., Ewa Kerc, and Mary D. Pato. Rat pulmonary arterial smooth muscle myosin light chain kinase and phosphatase activities decrease with age. Am J Physiol Lung Cell Mol Physiol 290: L509-L516, 2006. First published October 7, 2005 doi:10.1152/ajplung.00145.2005.-We and others have shown that the fetal pulmonary arterial smooth muscle potential for contraction and relaxation is significantly reduced compared with the adult. Whether these developmental changes relate to age differences in the expression and/or activity of key enzymes regulating the smooth muscle mechanical properties has not been previously evaluated. Therefore, we studied the catalytic activities and expression of myosin light chain kinase (MLCK) and myosin light chain phosphatase (MLCP) catalytic (PP1c␦) and regulatory (MYPT) subunits in late fetal, early newborn, and adult rat intrapulmonary arterial tissues. In keeping with the greater force development and relaxation of adult pulmonary artery, Western blot analysis showed that the MLCK, MYPT, and PP1c␦ contents increased significantly with age and were highest in the adult rat. In contrast, their specific activities (activity/enzyme content) were significantly higher in the fetal compared with the adult tissue. The fetal and newborn pulmonary arterial muscle relaxant response to the Rho-kinase inhibitor Y-27632 was greater than the adult tissue. In addition to the 130-kDa isoform of MLCK, we documented the presence of minor highermolecular-weight embryonic isoforms in the fetus and newborn. During fetal life, the lung pulmonary arterial MLCK-and MLCPspecific activities are highest and appear to be related to Rho-kinase activation during lung morphogenesis. lung; transitional circulation; pulmonary vascular resistance VASCULAR RESISTANCE IS dynamically controlled by the contraction and relaxation of its smooth muscle layer. Although this process is modulated by a number of humoral and nonhumoral factors, the vessel maximum potential for constriction and dilation is constrained by the vascular smooth muscle mechanical properties. We have previously shown that the pulmonary and systemic vascular smooth muscle of the newborn sheep has a lesser potential for force development, and a longer relaxation half-time compared with the adult (6, 9). Similar agerelated systemic vascular smooth muscle differences have been reported in relation to its maximum contraction in the rabbit (27) and rat (22), as well as to the degree of nitric oxideinduced relaxation in the guinea pig (5).The smooth muscle mechanical properties are primarily dependent on the rates of phosphorylation and dephosphorylation of the 20-kDa light chains of myosin by myosin light chain kinase (MLCK) and myosin light chain phosphatase (MLCP), respectively. These enzymes are key smooth muscle proteins that regulate contraction and relaxation, respectively. We have previously reported that prenatally induced pulmonary hypertension is associated with a significant reduction in pulmonary arterial MLCK and MLCP content (8). These findin...

show abstract

Decreased Phosphatase Activity, Increased Ca2+ Sensitivity, and Myosin Light Chain Phosphorylation in Urinary Bladder Smooth Muscle of Newborn Mice

Cited by 30 publications

References 27 publications

Neonatal mouse ileum: functional properties and protein composition of the contractile machinery

Neonatal mouse ileum: functional properties and protein composition of the contractile machinery

Potent Inhibition of Arterial Smooth Muscle Tonic Contractions by the Selective Myosin II Inhibitor, Blebbistatin

Rat pulmonary arterial smooth muscle myosin light chain kinase and phosphatase activities decrease with age

Contact Info

Product

Resources

About