scholarly journals Evidence that actomyosin cross bridges contribute to “passive” tension in detrusor smooth muscle

2010 ◽  
Vol 298 (6) ◽  
pp. F1424-F1435 ◽  
Author(s):  
Paul H. Ratz ◽  
John E. Speich
Keyword(s):  
Smooth Muscle ◽  
Actin Polymerization ◽  
Contractile Function ◽  
Cyclooxygenase Inhibitors ◽  
Passive Tension ◽  
Detrusor Smooth Muscle ◽  
Free Solution ◽  
Active Tension ◽  
Working Length ◽  
Cross Bridges

Contraction of detrusor smooth muscle (DSM) at short muscle lengths generates a stiffness component we termed adjustable passive stiffness (APS) that is retained in tissues incubated in a Ca2+-free solution, shifts the DSM length-passive tension curve up and to the left, and is softened by muscle strain and release (strain softened). In the present study, we tested the hypothesis that APS is due to slowly cycling actomyosin cross bridges. APS and active tension produced by the stimulus, KCl, displayed similar length dependencies with identical optimum length values. The myosin II inhibitor blebbistatin relaxed active tension maintained during a KCl-induced contraction and the passive tension maintained during stress-relaxation induced by muscle stretch in a Ca2+-free solution. Passive tension was attributed to tension maintaining rather than tension developing cross bridges because tension did not recover after a rapid 10% stretch and release as it did during a KCl-induced contraction. APS generated by a KCl-induced contraction in intact tissues was preserved in tissues permeabilized with Triton X-100. Blebbistatin and the actin polymerization inhibitor latrunculin-B reduced the degree of APS generated by a KCl-induced contraction. The degree of APS generated by KCl was inhibited to a greater degree than was the peak KCl-induced tension by rhoA kinase and cyclooxygenase inhibitors. These data support the hypothesis that APS is due to slowly cycling actomyosin cross bridges and suggest that cross bridges may play a novel role in DSM that uniquely serves to ensure proper contractile function over an extreme working length range.

scholarly journals Slowly cycling Rho kinase-dependent actomyosin cross-bridge “slippage” explains intrinsic high compliance of detrusor smooth muscle

2017 ◽  
Vol 313 (1) ◽  
pp. F126-F134 ◽  
Author(s):  
Christopher J. Neal ◽  
Jia B. Lin ◽  
Tanner Hurley ◽  
Amy S. Miner ◽  
John E. Speich ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Soft Tissues ◽  
Plastic Material ◽  
Rho Kinase ◽  
Detrusor Smooth Muscle ◽  
Display Time ◽  
Protein Activation ◽  
Cross Bridge ◽  
Cross Bridges ◽  
Dependent Viscosity

Biological soft tissues are viscoelastic because they display time-independent pseudoelasticity and time-dependent viscosity. However, there is evidence that the bladder may also display plasticity, defined as an increase in strain that is unrecoverable unless work is done by the muscle. In the present study, an electronic lever was used to induce controlled changes in stress and strain to determine whether rabbit detrusor smooth muscle (rDSM) is best described as viscoelastic or viscoelastic plastic. Using sequential ramp loading and unloading cycles, stress-strain and stiffness-stress analyses revealed that rDSM displayed reversible viscoelasticity, and that the viscous component was responsible for establishing a high stiffness at low stresses that increased only modestly with increasing stress compared with the large increase produced when the viscosity was absent and only pseudoelasticity governed tissue behavior. The study also revealed that rDSM underwent softening correlating with plastic deformation and creep that was reversed slowly when tissues were incubated in a Ca2+-containing solution. Together, the data support a model of DSM as a viscoelastic-plastic material, with the plasticity resulting from motor protein activation. This model explains the mechanism of intrinsic bladder compliance as “slipping” cross bridges, predicts that wall tension is dependent not only on vesicle pressure and radius but also on actomyosin cross-bridge activity, and identifies a novel molecular target for compliance regulation, both physiologically and therapeutically.

Increased responsiveness of jejunal longitudinal muscle in Trichinella-infected rats

1988 ◽  
Vol 254 (1) ◽  
pp. G124-G129 ◽  
Author(s):  
D. L. Vermillion ◽  
S. M. Collins
Keyword(s):  
Smooth Muscle ◽  
Muscle Function ◽  
Longitudinal Muscle ◽  
Trichinella Spiralis ◽  
Passive Tension ◽  
Active Tension ◽  
Maximum Tension ◽  
Longitudinal Smooth Muscle ◽  
Smooth Muscle Function

We examined in vitro changes in contractility of jejunal longitudinal muscle strips in rats infected with the nematode parasite Trichinella spiralis. Length-passive tension relationships were unchanged. However, muscle from infected rats on days 5 and 6 postinfection (PI) generated maximal active tension induced by carbachol at significantly less stretch (39.9 +/- 1.0 and 34.3 +/- 6.3%, respectively) than control tissues (66.0 +/- 2.3%). In infected rats on day 5 PI, the maximum tension generated by carbachol (1.6 +/- 0.4 g/mm2) and by 5-hydroxytryptamine (5-HTP) (2.6 +/- 0.1 g/mm2) was significantly greater than in control tissue (0.5 +/- 0.2 g/mm2). On removal of calcium from the medium, responses of muscle from control and infected rats were reduced in a proportionate manner. The increased responsiveness to carbachol and 5-HTP was maximal by day 5 PI and was associated with a decrease in the ED50 value for 5-HTP but not for carbachol. All changes were reversed by 23 days PI. These results indicate that T. spiralis infection in the rat is associated with alterations in jejunal longitudinal smooth muscle function.

Differential changes in ACh-, motilin-, substance P-, and K+-induced contractility in rabbit colitis

1999 ◽  
Vol 277 (1) ◽  
pp. G61-G68 ◽  
Author(s):  
Inge Depoortere ◽  
Gert van Assche ◽  
Theo Thijs ◽  
Karel Geboes ◽  
Theo L. Peeters
Keyword(s):  
Mechanical Properties ◽  
Smooth Muscle ◽  
Substance P ◽  
Contractile Activity ◽  
Passive Tension ◽  
Active Tension ◽  
Trinitrobenzenesulfonic Acid ◽  
Smooth Muscle Tissue ◽  
Structural Alterations ◽  
Time Profiles

To test the hypothesis that the changes in intestinal contractility, which accompany inflammation of the gut, are agonist specific, we compared the response of inflamed strips to substance P (SP), motilin, ACh, and K+ as a function of time. In parallel experiments, changes in the general mechanical properties (passive tension, optimal stretch) of the colitic tissue were evaluated. Colitis was induced by trinitrobenzenesulfonic acid, and rabbits were killed after 1, 2, 3, 5, or 8 days. Passive tension was increased starting from day 2 until day 8, and maximal active tension ( T max) was generated at less stretch from day 5. A 50% decrease in T max was observed for ACh and K+ between days 2 and 3 and for motilin and SP between days 3 and 5. For all compounds, T max returned to normal after 8 days. The pEC50value (negative logarithm of the concentration that induces 50% of the maximal contractile activity) for ACh was increased from day 3 until day 8 and for SP at day 3, whereas for motilin it was decreased at day 1. The changes in passive tension and optimal stretch indicate generalized structural alterations of smooth muscle tissue. However, the different time profiles of the changes in active tension and contractile potency for different contractile agents suggest that inflammation specifically affects receptor-mediated mechanisms.

The length-tension relationship of the dorsal longitudinal muscle of a leech

1975 ◽  
Vol 62 (1) ◽  
pp. 43-53
Author(s):  
JB Miller
Keyword(s):  
Body Wall ◽  
Longitudinal Muscle ◽  
Muscle Fibres ◽  
Passive Tension ◽  
Active Tension ◽  
Thin Filaments ◽  
Thick Filaments ◽  
Tension Curve ◽  
Cross Bridges ◽  
Relationship Of

The length-tension relationship of a preparation of the dorsal body wall of the leech Haemopis sanguisuga was determined. Passive tension is low except at very long lengths of the preparation, when it rises steeply. It is due mainly to the epidermis present in the preparation. The active tension curve is very flat, with tension being reduced only at very short and very long lengths. This shape is explained in the context of the myofilament arrangement of the muscle fibres. It may be that thin filaments can form cross-bridges with different thick filaments at different lengths of the preparation.

scholarly journals The effects of the small GTPase RhoA on the muscarinic contraction of airway smooth muscle result from its role in regulating actin polymerization

2010 ◽  
Vol 299 (2) ◽  
pp. C298-C306 ◽  
Author(s):  
Wenwu Zhang ◽  
Liping Du ◽  
Susan J. Gunst
Keyword(s):  
Smooth Muscle ◽  
Airway Smooth Muscle ◽  
Actin Polymerization ◽  
Kinase Inhibitor ◽  
Cell Types ◽  
Small Gtpase ◽  
Calyculin A ◽  
Active Tension ◽  
Tension Generation ◽  
Mlc Phosphorylation

The small GTPase RhoA increases the Ca2+ sensitivity of smooth muscle contraction and myosin light chain (MLC) phosphorylation by inhibiting the activity of MLC phosphatase. RhoA is also a known regulator of cytoskeletal dynamics and actin polymerization in many cell types. In airway smooth muscle (ASM), contractile stimulation induces MLC phosphorylation and actin polymerization, which are both required for active tension generation. The objective of this study was to evaluate the primary mechanism by which RhoA regulates active tension generation in intact ASM during stimulation with acetylcholine (ACh). RhoA activity was inhibited in canine tracheal smooth muscle tissues by expressing the inactive RhoA mutant, RhoA T19N, in the intact tissues or by treating them with the cell-permeant RhoA inhibitor, exoenzyme C3 transferase. RhoA inactivation reduced ACh-induced contractile force by ∼60% and completely inhibited ACh-induced actin polymerization but inhibited ACh-induced MLC phosphorylation by only ∼20%. Inactivation of MLC phosphatase with calyculin A reversed the reduction in MLC phosphorylation caused by RhoA inactivation, but calyculin A did not reverse the depression of active tension and actin polymerization caused by RhoA inactivation. The MLC kinase inhibitor, ML-7, inhibited ACh-induced MLC phosphorylation by ∼80% and depressed active force by ∼70% but did not affect ACh-induced actin polymerization, demonstrating that ACh-stimulated actin polymerization occurs independently of MLC phosphorylation. We conclude that the RhoA-mediated regulation of ACh-induced contractile tension in ASM results from its role in mediating actin polymerization rather than from effects on MLC phosphatase or MLC phosphorylation.

Mechanical properties of isolated smooth muscle from human rectum and internal anal sphincter

1993 ◽  
Vol 265 (4) ◽  
pp. G792-G798 ◽  
Author(s):  
E. B. Glavind ◽  
A. Forman ◽  
G. Madsen ◽  
D. Svane ◽  
K. E. Andersson ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Anal Sphincter ◽  
Internal Anal Sphincter ◽  
Muscle Layer ◽  
Isometric Tension ◽  
Passive Tension ◽  
Active Tension ◽  
Active Length ◽  
Circular Smooth Muscle ◽  
Resting Tension

The passive and active length-tension relations of the circular smooth muscle layer of the human distal rectum and the proximal and distal internal anal sphincter were investigated. Muscle strips were prepared and mounted in organ baths for recording of isometric tension. Resting lengths (LR) were measured, and the preparations were elongated stepwise. At each length, the corresponding values for passive tension, spontaneous active resting tension, and the submaximal active tension were recorded. Elongations of 200-380% of LR were possible before a sharp increase in passive tension occurred. None of the mean tension values measured at length for maximal active tension (LO) differed significantly among the three muscle types. All strips developed active resting tension. This tension was myogenic and contributed 10 +/- 3, 23 +/- 6, and 27 +/- 6% to the total active performance of rectal and proximal and distal sphincter preparations, respectively. Collagen constituted approximately 50% of smooth muscle biopsies, with highest contents in distal internal anal sphincter. This study provides an acceptable method for assessing the optimal experimental length by stretching the strips in an inactive state to 200% of LR, followed by individual adjustment of the passive tension to 5 mN/mm2 measured at 200% of LR

257: The Phosphodiesterase Type 4 Inhibitor, Rolipram, is More Efficient to Relax Detrusor Smooth Muscle in Rats with Overactive Bladder than in Control Rats

2007 ◽  
Vol 177 (4S) ◽  
pp. 86-86
Author(s):  
Stephanie Oger ◽  
Delphine Behr-Roussel ◽  
Katell Mevel ◽  
Jacques Bernabe ◽  
Pierre Denys ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Overactive Bladder ◽  
Detrusor Smooth Muscle ◽  
Phosphodiesterase Type
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