Comprehensive Physiology Wiley Online Library

Mechanical properties of gastrointestinal smooth muscle

Full Article on Wiley Online Library



Abstract

The sections in this article are:

1 Classic Mechanical Characterization of Muscle
1.1 Controlling the Conditions of Contraction
2 Mechanism of Contraction of Skeletal Muscle
2.1 Basic Concepts of Skeletal Muscle Contraction
3 Classic Mechanical Concepts Applied to Smooth Muscle
3.1 Isometric Mechanical Behavior
3.2 Isotonic Mechanical Behavior
3.3 Other Special Mechanical Considerations
4 Comparative Aspects of Smooth Muscle Mechanical Properties
5 Experimental Approaches to Gastrointestinal Muscle Mechanics
5.1 Direct Study of Gut Movements and Motility
5.2 Study of Isolated Muscle Preparations
5.3 Instrumentation Used to Study Smooth Muscle Mechanics
6 Mechanical Properties of Gastrointestinal Smooth Muscle
6.1 Isometric Properties
6.2 Isotonic Properties
6.3 Relaxation of Smooth Muscle
7 Appendix
7.1 Intuitive Approach to Behavior of Viscoelastic Systems
Figure 1. Figure 1.

Length‐tension properties of various smooth muscles. A: single cells from Bufo marinus stomach show broad active length‐tension curve (points on right, single values; multiple values obtained at shorter lengths.) Passive force (lower points) was negligible. B: behavior of rabbit taenia coli. There is large resting tension at optimum length. C: bovine trachealis muscle shows little passive tension at optimal length. D: hog carotid artery has somewhat more passive force. E: cat duodenal circular muscle has very high resting tension when highly stretched.

A from Fay ; B from Gordon and Siegman ; C from Kamm and Stull ; D from Herlihy and Murphy , by permission of the American Heart Association, Inc.; E from Meiss
Figure 2. Figure 2.

Mechanical analogs for explaining muscle functions. A: simplest (two‐component) model, consisting of contractile component and series elastic component. B, C: addition of parallel elastic component is required to account for resting elastic properties.

Figure 3. Figure 3.

Typical transducers used in muscle research. A: length (or position) transducer, in conjunction with light‐weight lever, allows muscle length to be set (via preload stop) and isotonic force to be set (via afterload weight). Fulcrum is offset and lever is made as light as possible to reduce inertial effects. Position detector with considerable range of linearity is used to sense lever position. B: force (or tension) transducer. Rigid lever is replaced with stiff but flexible cantilever beam that is bent slightly by muscle force. Very sensitive position detector senses small deflection of cantilever. See FORCE TRANSDUCERS, p. 278, for special design considerations that optimize performance of transducers. Moving member of transducer partially interrupts light falling on photodetector; these variations are converted into electrical output. C: position detector details common to both types.

Figure 4. Figure 4.

Physical and electronic arrangements for studying muscle mechanical function. A: vertical arrangement allowing simultaneous measurement of force and shortening. Force transducer connection passes through low‐friction liquid‐tight seal in bottom of chamber. B: horizontal arrangement in which muscle length is controlled electronically. Various types of feedback circuitry can allow either force or length to be controlled for specific experimental purposes.

A adapted from Meiss ; B from Meiss
Figure 5. Figure 5.

Use of aequorin luminescence to follow changes in intracellular Ca2+ activity in smooth muscle. A: Ca2+ signal from single cell from toad stomach (Bufo marinus) microinjected with aequorin. Simultaneous stimulus and membrane potential measurements are shown. Mechanical activity begins where indicated, after peak Ca2+ signal has declined. B: Ca2+ signal from strip of ferret portal vein smooth muscle, chemically loaded with aequorin and stimulated with single brief electrical shock. (Upper trace is light output, lower trace is force.) Peak light output occurs during rising phase of twitch (cf. A). C: chemically stimulated aequorin‐loaded ferret gastric fundus smooth muscle undergoes prolonged contraction despite fall in Ca2+ signal. (Upper trace is force, lower trace is light output.)

A from Fay et al. , reprinted by permission from Nature, copyright 1979, Macmillan Journals Limited; B from Morgan and Morgan ; C from Morgan and Morgan
Figure 6. Figure 6.

Schematic of smooth muscle myosin molecule. Light meromyosin (LMM) segment forms filamentous portion of aggregated myosin, whereas heavy meromyosin (HMM) contains active biochemical and mechanical functions. Globular (dual) head portion contains light chains that are phosphorylated to initiate ATPase activity.

From Kendrick‐Jones and Scholey
Figure 7. Figure 7.

Proposed pathways regulating smooth muscle contraction cycle. A: activation occurs when Ca2+ is bound to calmodulin (CM), which then activates myosin light‐chain kinase (MLCK), leading to phosphorylation of myosin and subsequent muscle contraction. In‐activation depends on removal of Ca2+ from CM, reducing activity of MLCK. Endogenous myosin phosphatase de‐phosphorylates myosin, leading to relaxation. B: similar scheme, which also allows for modulation of cycling of active crossbridges by varying internal Ca2+ levels (lower right); it also allows for presence of resting, attached crossbridges (lower center) at lower Ca2+ levels and for resting, detached crossbridges (lower left) at extremely low Ca2+ levels.

A from Kamm and Stull , reproduced, with permission, from the Annual Review of Pharmacology and Toxicology, volume 25, © 1985 by Annual Reviews Inc.; B from Siegman et al.
Figure 8. Figure 8.

Relationship between Ca2+ activity and isometric force in chemically skinned smooth muscle. A: rabbit taenia coli skinned with Triton X‐100. Open circles, force in presence of 6.9 mM Mg2+; closed circles, increased Ca2+ sensitivity in presence of 1.0 mM Mg2+. B: guinea pig taenia coli skinned with Triton X‐100. Center curve, skinned muscle; right curve, intact muscle stimulated chemically. Addition of 1 μM calmodulin increases Ca2+ sensitivity (left curve). Both ordinates are in units of relative force; abscissa, logarithmic scale of Ca2+ activity.

A adapted from Gordon , B from Arner
Figure 9. Figure 9.

Relation between active force and stiffness in various intact smooth muscles measured by variety of techniques. Note linearity of relationship. A: schematic of 3 techniques used for measurement. Left, small rapid shortening produces small fall in isometric force and ratio of change in force to change in length (ΔP/ΔL) expresses stiffness. Center, stiffness is computed from slopes of length and force curves at points of isometric‐isotonic transition. Right, release from isometric force to isotonic an isometric load provides the ΔP/ΔL information. B: rabbit urinary bladder muscle stiffness depends slightly on method of measurement; open circles, from isometric‐to‐isotonic transitions (cf. A, center); closed circles, values obtained by small isometric quick releases (cf. A, left). C: stiffness of dogfish spiral intestine rotator muscle measured by taking initial slope of long, constant‐velocity stretches (cf. Fig. C). D: stiffness throughout contraction‐relaxation cycle of rabbit mesotubarium muscle measured continuously with small oscillatory length perturbations and resolved into its elastic and viscous components. At same force muscle is stiffer during relaxation than during contraction. E: stiffness of single Bufo marinus stomach muscle cell measured by small stretches and releases (upper inset). Ordinate, expression of active stiffness; abscissa, expression of active force.

A and B reprinted from Hellstrand , by courtesy of Marcell Dekker, Inc.; C from Meiss et al. ; D from Meiss ; and E from Warshaw and Fay
Figure 10. Figure 10.

Behavior of active smooth muscle subjected to large stretches. A: canine airway muscle subjected to repeated cyclic stretches and releases. On initial stretch (uppermost trace) marked yielding was followed by linear force increase. B: cat duodenal muscle stretched with single sinusoidal cycles. During rise of force slope was rate independent, during relaxation rapid stretch produced higher slope. C: rabbit mesotubarium muscle stretched with linear ramp function. Initial force step before marked yielding depended on developed force but long‐range slope did not. Stretch during relaxation produced larger initial force steps and lower long‐range slopes. D: rat portal vein showed initial step that depended on speed of stretch and long‐range slope that did not (rates increased in traces 1–4 over range 0.03–1.5 mm/s). P, force exerted.

A from Gunst , B adapted from Meiss , C from Meiss , D from Johansson
Figure 11. Figure 11.

Representative smooth muscle force‐velocity curves. Several means of analysis are shown. A: from cat duodenal circular muscle. B: from hog carotid artery. C: from rat portal vein. Afterloaded isotonic contractions (open circles) produced lower velocity values than those from isotonic quick releases (closed circles). D: from rabbit taenia coli muscle. Note reversed axes. P, force exerted; P0, maximum tetanic isometric force; a, constant (force dimensions); 6, constant (velocity dimensions); V, velocity of shortening; Vmax, maximum velocity of shortening.

A from Meiss , B from Herlihy and Murphy , C from Hellstrand and Johansson , D from Gordon and Siegman
Figure 12. Figure 12.

Changes in shortening velocity (V) with time. A: bovine trachealis muscle force is maintained while shortening velocity (V0) falls with duration of contraction. B: similar phenomenon in carotid arterial smooth muscle. F, force; F0, maximal force at optimum length. C: in rabbit taenia coli velocity of shortening falls markedly while force and myosin phosphorylation are maintained.

A from Kamm and Stull , B from Dillon and Murphy , C from Siegman et al.
Figure 13. Figure 13.

Phenomena associated with smooth muscle relaxation. A: in cat duodenal circular muscle isotonic shortening prolongs isometric relaxation in proportion to its amount. Lower pair of traces, prolongation of relaxation is associated with early isotonic shortening. No length traces are shown here. B: maximum force potential of tracheal smooth muscle persists long after isometric relaxation is complete. C: augmented stretch resistance (ASR) of cat duodenal circular muscle is revealed (uppermost trace) by comparing force responses to identical stretches before and after contraction. Level of ASR is set by preceding contractile activity (center set of traces). ASR is discharged quantitatively by maintained stretch (lower set of traces).

A from R. A. Meiss, unpublished observations; B reprinted from Stephens et al. , by courtesy of Marcel Dekker, Inc.; C adapted from Meiss


Figure 1.

Length‐tension properties of various smooth muscles. A: single cells from Bufo marinus stomach show broad active length‐tension curve (points on right, single values; multiple values obtained at shorter lengths.) Passive force (lower points) was negligible. B: behavior of rabbit taenia coli. There is large resting tension at optimum length. C: bovine trachealis muscle shows little passive tension at optimal length. D: hog carotid artery has somewhat more passive force. E: cat duodenal circular muscle has very high resting tension when highly stretched.

A from Fay ; B from Gordon and Siegman ; C from Kamm and Stull ; D from Herlihy and Murphy , by permission of the American Heart Association, Inc.; E from Meiss


Figure 2.

Mechanical analogs for explaining muscle functions. A: simplest (two‐component) model, consisting of contractile component and series elastic component. B, C: addition of parallel elastic component is required to account for resting elastic properties.



Figure 3.

Typical transducers used in muscle research. A: length (or position) transducer, in conjunction with light‐weight lever, allows muscle length to be set (via preload stop) and isotonic force to be set (via afterload weight). Fulcrum is offset and lever is made as light as possible to reduce inertial effects. Position detector with considerable range of linearity is used to sense lever position. B: force (or tension) transducer. Rigid lever is replaced with stiff but flexible cantilever beam that is bent slightly by muscle force. Very sensitive position detector senses small deflection of cantilever. See FORCE TRANSDUCERS, p. 278, for special design considerations that optimize performance of transducers. Moving member of transducer partially interrupts light falling on photodetector; these variations are converted into electrical output. C: position detector details common to both types.



Figure 4.

Physical and electronic arrangements for studying muscle mechanical function. A: vertical arrangement allowing simultaneous measurement of force and shortening. Force transducer connection passes through low‐friction liquid‐tight seal in bottom of chamber. B: horizontal arrangement in which muscle length is controlled electronically. Various types of feedback circuitry can allow either force or length to be controlled for specific experimental purposes.

A adapted from Meiss ; B from Meiss


Figure 5.

Use of aequorin luminescence to follow changes in intracellular Ca2+ activity in smooth muscle. A: Ca2+ signal from single cell from toad stomach (Bufo marinus) microinjected with aequorin. Simultaneous stimulus and membrane potential measurements are shown. Mechanical activity begins where indicated, after peak Ca2+ signal has declined. B: Ca2+ signal from strip of ferret portal vein smooth muscle, chemically loaded with aequorin and stimulated with single brief electrical shock. (Upper trace is light output, lower trace is force.) Peak light output occurs during rising phase of twitch (cf. A). C: chemically stimulated aequorin‐loaded ferret gastric fundus smooth muscle undergoes prolonged contraction despite fall in Ca2+ signal. (Upper trace is force, lower trace is light output.)

A from Fay et al. , reprinted by permission from Nature, copyright 1979, Macmillan Journals Limited; B from Morgan and Morgan ; C from Morgan and Morgan


Figure 6.

Schematic of smooth muscle myosin molecule. Light meromyosin (LMM) segment forms filamentous portion of aggregated myosin, whereas heavy meromyosin (HMM) contains active biochemical and mechanical functions. Globular (dual) head portion contains light chains that are phosphorylated to initiate ATPase activity.

From Kendrick‐Jones and Scholey


Figure 7.

Proposed pathways regulating smooth muscle contraction cycle. A: activation occurs when Ca2+ is bound to calmodulin (CM), which then activates myosin light‐chain kinase (MLCK), leading to phosphorylation of myosin and subsequent muscle contraction. In‐activation depends on removal of Ca2+ from CM, reducing activity of MLCK. Endogenous myosin phosphatase de‐phosphorylates myosin, leading to relaxation. B: similar scheme, which also allows for modulation of cycling of active crossbridges by varying internal Ca2+ levels (lower right); it also allows for presence of resting, attached crossbridges (lower center) at lower Ca2+ levels and for resting, detached crossbridges (lower left) at extremely low Ca2+ levels.

A from Kamm and Stull , reproduced, with permission, from the Annual Review of Pharmacology and Toxicology, volume 25, © 1985 by Annual Reviews Inc.; B from Siegman et al.


Figure 8.

Relationship between Ca2+ activity and isometric force in chemically skinned smooth muscle. A: rabbit taenia coli skinned with Triton X‐100. Open circles, force in presence of 6.9 mM Mg2+; closed circles, increased Ca2+ sensitivity in presence of 1.0 mM Mg2+. B: guinea pig taenia coli skinned with Triton X‐100. Center curve, skinned muscle; right curve, intact muscle stimulated chemically. Addition of 1 μM calmodulin increases Ca2+ sensitivity (left curve). Both ordinates are in units of relative force; abscissa, logarithmic scale of Ca2+ activity.

A adapted from Gordon , B from Arner


Figure 9.

Relation between active force and stiffness in various intact smooth muscles measured by variety of techniques. Note linearity of relationship. A: schematic of 3 techniques used for measurement. Left, small rapid shortening produces small fall in isometric force and ratio of change in force to change in length (ΔP/ΔL) expresses stiffness. Center, stiffness is computed from slopes of length and force curves at points of isometric‐isotonic transition. Right, release from isometric force to isotonic an isometric load provides the ΔP/ΔL information. B: rabbit urinary bladder muscle stiffness depends slightly on method of measurement; open circles, from isometric‐to‐isotonic transitions (cf. A, center); closed circles, values obtained by small isometric quick releases (cf. A, left). C: stiffness of dogfish spiral intestine rotator muscle measured by taking initial slope of long, constant‐velocity stretches (cf. Fig. C). D: stiffness throughout contraction‐relaxation cycle of rabbit mesotubarium muscle measured continuously with small oscillatory length perturbations and resolved into its elastic and viscous components. At same force muscle is stiffer during relaxation than during contraction. E: stiffness of single Bufo marinus stomach muscle cell measured by small stretches and releases (upper inset). Ordinate, expression of active stiffness; abscissa, expression of active force.

A and B reprinted from Hellstrand , by courtesy of Marcell Dekker, Inc.; C from Meiss et al. ; D from Meiss ; and E from Warshaw and Fay


Figure 10.

Behavior of active smooth muscle subjected to large stretches. A: canine airway muscle subjected to repeated cyclic stretches and releases. On initial stretch (uppermost trace) marked yielding was followed by linear force increase. B: cat duodenal muscle stretched with single sinusoidal cycles. During rise of force slope was rate independent, during relaxation rapid stretch produced higher slope. C: rabbit mesotubarium muscle stretched with linear ramp function. Initial force step before marked yielding depended on developed force but long‐range slope did not. Stretch during relaxation produced larger initial force steps and lower long‐range slopes. D: rat portal vein showed initial step that depended on speed of stretch and long‐range slope that did not (rates increased in traces 1–4 over range 0.03–1.5 mm/s). P, force exerted.

A from Gunst , B adapted from Meiss , C from Meiss , D from Johansson


Figure 11.

Representative smooth muscle force‐velocity curves. Several means of analysis are shown. A: from cat duodenal circular muscle. B: from hog carotid artery. C: from rat portal vein. Afterloaded isotonic contractions (open circles) produced lower velocity values than those from isotonic quick releases (closed circles). D: from rabbit taenia coli muscle. Note reversed axes. P, force exerted; P0, maximum tetanic isometric force; a, constant (force dimensions); 6, constant (velocity dimensions); V, velocity of shortening; Vmax, maximum velocity of shortening.

A from Meiss , B from Herlihy and Murphy , C from Hellstrand and Johansson , D from Gordon and Siegman


Figure 12.

Changes in shortening velocity (V) with time. A: bovine trachealis muscle force is maintained while shortening velocity (V0) falls with duration of contraction. B: similar phenomenon in carotid arterial smooth muscle. F, force; F0, maximal force at optimum length. C: in rabbit taenia coli velocity of shortening falls markedly while force and myosin phosphorylation are maintained.

A from Kamm and Stull , B from Dillon and Murphy , C from Siegman et al.


Figure 13.

Phenomena associated with smooth muscle relaxation. A: in cat duodenal circular muscle isotonic shortening prolongs isometric relaxation in proportion to its amount. Lower pair of traces, prolongation of relaxation is associated with early isotonic shortening. No length traces are shown here. B: maximum force potential of tracheal smooth muscle persists long after isometric relaxation is complete. C: augmented stretch resistance (ASR) of cat duodenal circular muscle is revealed (uppermost trace) by comparing force responses to identical stretches before and after contraction. Level of ASR is set by preceding contractile activity (center set of traces). ASR is discharged quantitatively by maintained stretch (lower set of traces).

A from R. A. Meiss, unpublished observations; B reprinted from Stephens et al. , by courtesy of Marcel Dekker, Inc.; C adapted from Meiss
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Richard A. Meiss. Mechanical properties of gastrointestinal smooth muscle. Compr Physiol 2011, Supplement 16: Handbook of Physiology, The Gastrointestinal System, Motility and Circulation: 273-329. First published in print 1989. doi: 10.1002/cphy.cp060108