Twitch potentiation of frog (Rana japonica) skeletal muscle by antipyrine

1989 ◽  
Vol 92 (1) ◽  
pp. 61-65
Author(s):  
Naoji Fujishiro ◽  
Hiroshi Kawata
Keyword(s):  
Skeletal Muscle ◽  
Rana Japonica ◽  
Twitch Potentiation

Effects of pH on the length-dependent twitch potentiation in skeletal muscle

2002 ◽  
Vol 92 (3) ◽  
pp. 1293-1299 ◽  
Author(s):  
Dilson E. Rassier ◽  
Walter Herzog
Keyword(s):  
Skeletal Muscle ◽  
Force Production ◽  
Optimal Length ◽  
Twitch Potentiation ◽  
Length Dependence ◽  
Charge Potential ◽  
Before And After ◽  
Effects Of Ph ◽  
Isometric Twitch

When muscle is elongated, there is a length dependence of twitch potentiation and an increased Ca2+ sensitivity of the myofilaments. Changes in the charge potential of myofilaments, induced by a decrease in pH, are known to abolish the length dependence of Ca2+ sensitivity. This study was aimed at testing the hypothesis that a decrease in pH, and the concomitant loss of length dependence of Ca2+sensitivity, depresses the length dependence of staircase potentiation. In vitro, isometric twitch contractions of fiber bundles dissected from the mouse extensor digitorum longus, performed before and after 10 s of 10-Hz stimulation (i.e., the staircase potentiation protocol) were analyzed at five different lengths, ranging from optimal length for maximal force production ( L o; = 12 ± 0.7 mm) to L o + 1.2 mm ( L o + 10%). These measurements were made at an extracellular pH of 6.6, 7.4, and 7.8 (pH changes induced by altering the CO2 concentration of the bath solution). At pH 7.4 and 7.8, the degree of potentiation after 10-Hz stimulation showed a linear decrease with increased fiber bundle length ( r 2 = 0.95 and r 2 = 0.99, respectively). At pH 6.6, the length dependence of potentiation was abolished, and the slope of the length-potentiation relationship was not different from zero ( r 2 = 0.05). The results of this study indicate that length dependence of potentiation in intact skeletal muscle is abolished by lowering the pH. Because decreasing the pH decreases Ca2+ sensitivity and changes the charge potential of the filaments, the mechanism of length-dependent potentiation may be closely related to the length dependence of Ca2+sensitivity, and changes in the charge potential of the myofilaments may be important in regulating this relationship.

Effects of deuterium oxide on mechanics and energetics of skeletal muscle contraction

1980 ◽  
Vol 239 (3) ◽  
pp. C105-C111
Author(s):  
J. A. Rall
Keyword(s):  
Skeletal Muscle ◽  
Deuterium Oxide ◽  
Energy Liberation ◽  
Twitch Force ◽  
Force Development ◽  
Twitch Potentiation ◽  
Skeletal Muscle Contraction ◽  
Per Se ◽  
Activation Heat ◽  
Normal Ringer

Mechanics and energetics of contraction were studied in isolated frog semitendinosus muscles (n = 15) in deuterium oxide (D2O) at 5 degrees C. Twitch force and energy liberation (heat + work) in 99.8% D2O-Ringer at lo were 4 +/- 0.8 and 22 +/- 1%, respectively, of control values. Tetanus force was slowed in development, and developed tetanus force was reduced to 89 +/- 7% of control values. With repeated tetanic contractions, the rate of force development increased, and peak force increased above control values in some muscles. The twitch was potentiated 10-fold (10 +/- 2) after repeated tetanic contractions. Energy liberation increased but not in proportion to force. Ca2+ cycling energy liberation or activation heat, estimated from stretched muscles, was 60 +/- 3% of control values. With maximum posttetanic twitch potentiation, the activation heat increased by 25 +/- 3%. Peak twitch force and energy liberation occurred at longer muscle lengths than in normal Ringer. After correcting for small differences in force development at lo and 1.38 +/- 0.01 lo, it was possible to estimate the effect of length per se on energy liberation. Under these conditions, there was an 8 +/- 2% decrease in energy liberation at 1.38 lo.

Effect of temperature on myosin phosphorylation in mouse skeletal muscle

1990 ◽  
Vol 259 (3) ◽  
pp. C432-C438 ◽  
Author(s):  
R. L. Moore ◽  
B. M. Palmer ◽  
S. L. Williams ◽  
H. Tanabe ◽  
R. W. Grange ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Light Chain ◽  
Incubation Temperature ◽  
Effect Of Temperature ◽  
Contractile Element ◽  
Mammalian Skeletal Muscle ◽  
Phosphate Content ◽  
Intact Mouse ◽  
Twitch Potentiation ◽  
Isometric Twitch

The effect of muscle contraction on phosphorylatable myosin light chain (P-light chain) phosphate content and isometric twitch tension was examined at 25, 30, and 35 degrees C in intact mouse extensor digitorum longus muscle. Peak tetanic tension was unaffected by temperature, whereas peak unpotentiated isometric twitch tension was inversely proportional to muscle incubation temperature. The extent of phosphate incorporation into P-light chain elicited by a 20-s train of twitches (5/s) was inversely proportional to muscle incubation temperature, whereas the fractional increase in twitch tension (twitch potentiation) elicited by repetitive stimulation was directly proportional to muscle incubation temperature. After the twitch train, the rate of decline of potentiated twitch tension and of P-light chain dephosphorylation was directly proportional to muscle incubation temperature. The net result was that a significant and unique relationship between P-light chain phosphate content and contraction-induced tension potentiation existed at each temperature examined. The slope of the P-light chain phosphate vs. isometric twitch potentiation relationship varied directly as a function of muscle incubation temperature. The observations that the slope of this relationship increases and that unpotentiated twitch tension decreases when muscle incubation temperature is increased support the hypothesis that contraction-induced tension potentiation in intact mammalian skeletal muscle is the result of a sensitization of the contractile element to activation by Ca2+ that is brought about by P-light chain phosphorylation.

A comparison of the effects of cationic, anionic, and neutral amphipathic agents on the contractile behaviour of frog skeletal muscle. I. Twitches and potential threshold for contraction

1984 ◽  
Vol 62 (12) ◽  
pp. 1348-1355
Author(s):  
James G. Foulks ◽  
Lillian Morishita
Keyword(s):  
Skeletal Muscle ◽  
Hydrophobic Interactions ◽  
Contractile Function ◽  
Divalent Cations ◽  
Frog Skeletal Muscle ◽  
Twitch Potentiation ◽  
Low Concentrations ◽  
Small N ◽  
Potential Threshold ◽  
Caffeine Contractures

Cationic, anionic, and neutral amphipathic agents displayed striking differences as well as similarities in their effects on the contractile function of frog skeletal muscle. Slowed repolarization during the action potential appeared to account for twitch potentiation by low concentrations of alkyl trimethylammonium and by small n-alkanols (propanol, butanol). Small n-alkanols also caused a decrease in the potential threshold for K contractures and slower relaxation of submaximum K contractures as well as enhancement of chloride withdrawal and caffeine contractures, but these effects were not observed with larger alkanols. For the ionic amphipathic agents, the direction of the changes in the relation between K0 and K-contracture tension could be accounted for on the basis of the expected changes in surface charge, but the effects of these two types of agents on the rate of relaxation of submaximum K contractures were disproportionate and with the cationic series were opposite in direction to those produced by inorganic divalent cations. The reductions in the amplitude of chloride-withdrawal contractures by cationic as well as anionic amphipaths indicated that both types of agents can impair excitation–contraction coupling. Similar depressant effects on caffeine contractures demonstrate that these responses also can be influenced by events restricted to the external lamina of the sarcolemma. It is concluded that opposite effects can be produced by similar perturbations in different regions of the sarcolemma and that electrostatic as well as hydrophobic interactions can make an important contribution to the effects of amphipathic agents on twitches and contractures in skeletal muscle.

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