Isometric tension

FIGURE 2.18 Inotropic and lusitropic responses of guinea pig left atria to (3-adrenoceptor stimulation. Panels A to C isometric tension waveforms of cardiac contraction (ordinates are mg tension abscissae are msec), (a) Effect of 0.3 nM isoproterenol on the waveform. The wave is shortened due to an increase in the rate of diastolic relaxation, whereas no inotropic response (change in peak tension) is observed at this concentration, (b) A further shortening of waveform duration (lusitropic response) is observed with 3 nM isoproterenol. This is concomitant with positive inotropic response (increase maximal tension), (c) This trend continues with 100 nM isoproterenol, (d) Dose-response curves for ino tropy (filled circles) and lusitropy (open circles) in guinea pig atria for isoproterenol, (e) Dose-response curves for inotropy (filled circles) and lusitropy (open circles) in guinea pig atria for the P-adrenoceptor partial agonist prenalterol. Data redrawn from [6]. 

Gordon, A.M., Huxley, A.F., Julian, F.J. (1966). The variation in isometric tension with sarcomere length in vertebrate muscle fibers. J. Physiol. 184, 170-192. 

Adhikari BB, Wang K. 2001. S100A1 modulates skeletal muscle contraction by desensitizing calcium activation of isometric tension, stiffness and ATPase. FEBS Lett 497(2, 3) 95-98. 

Bumstock et al. (1978) used recorded isometric tension of mucosal-free strips of the detrusor of the bladder from guinea pigs in vitro after electrical field stimulation. 

In an in vitro experiment using uterine muscle strips from 10 consenting parturients undergoing cesarean section, therapeutic concentrations of propofol had no effect on isometric tension developed during contraction of the muscle (68). However, higher than therapeutic concentrations did reduce the peak muscle tension that developed. These results confirm that propofol is free of this adverse effect, which is a known cause of postpartum bleeding after the use of volatile anesthetic drugs. 

The etiology of the acute kidney injury may be related to isometric tension in restrained limbs or to ischemic damage to muscle in the presence of hyperthermia and/or limb compression [161, 166]. While it is possible that the drug itself may possess direct myopathic toxicity when abused in certain settings, it does not induce rhabdomyolysis in unrestrained animals [167]. Animals restrained in immobilizing cages, however, develop rhabdomyolysis, which correlates with isometric muscle tension during the restrained period which can be prevented by prior denervation [167]. 

Figure 16.23 Pharmacological setup for isometric tension (contractility) recordings of isolated smooth muscle preparations under the influence of ion channel modulators (inhibitors and activators). Smooth muscle strips (as visible on the second enlarged picture) or rings are placed in thermostatically controlled tissue baths and are connected to a force displacement transducer for isometric recording. The force signal (contractions) is recorded electronically via specialized software and displayed on a monitor.

Caldesmon has been shown to reduce isometric tension in chemically skinned smooth or skeletal muscle fibers, thus clearly suggesting that it can influence contractility (Szpacenko et al., 1985 Pfitzer et al.. 

The structure of the contractile unit is fundamental to the interpretation of the relationship between muscle length and isometric tension in skeletal muscle. Each sarcomere unit contains bipolar thick filaments with a central bare zone surrounded by pairs of actin filaments of opposite polarity. The actin filaments are anchored at Z-bands that are aligned in parallel. The length-tension behavior of skeletal muscle has been interpreted in terms of changes in the overlap between the thick eind thin filaments as... 

Gordon AL, Huxley AF, Julian FJ (1966) The variation of isometric tension with sarcomere length in vertebrate muscle fibres. J Physiol 184 170192 Gordon DJ, Boyer JL, Korn ED (1977) Comparative biochemistry of non-muscle actins. J Biol Chem 252 83008309... 

Cassidy PS, Kerrick WG, Hoar PE, Malencik DA (1981) Exogenous calmodulin increases Ca " sensitivity of isometric tension activation and myosin phosphorylation in skinned smooth muscle. Pflugers Arch 392 115-120 Cavaille F, Janmot C, Ropert S, d Albis A (1986) Isoforms of myosin and actin in human, monkey and rat myometrium.Comparison of pregnant and non-preghant uterus proteins. Eur J Biochem 160 507-513... 

Goeckeler ZM, Wysolmerski RB Myosin light chain kinase-regulated endothelial cell contraction The relationship between isometric tension, actin polymerization, and myosin phosphorylation. J Cell Biol 1995 130 613-627. 

Isometric — tension develops in a muscle, but the muscle length does not change and no movement occurs. 

A. M. Gordon, A. F. Huxley, and F. J. Julian, The Variation in Isometric Tension with Sarcomere Length in Vertebrate Muscle Fibers, J. Physiol 184, 170-192 (1966). 

Allain, J.S. etal. Isometric Tension Developed During Heating of Collagenous Tissues, Relationships with Collagen Crosslinking, Biochemica et Biophpysica Acta. 533 147-255 (1978). 

In 1970, Hill described the same properties for intact frog sartorius muscle." Hill reported a linear increase in isometric tension on raising the temperature from 0° to 23° C, but on raising the temperature higher there occurred a more... 

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