Studies of the excitation-contraction mechanism in the skeletal muscle and the myocardium

Edman, K. A. P.; Grieve, D. W.; Nilsson, Erik

doi:10.1007/bf00363311

Cited by 52 publications

(22 citation statements)

References 18 publications

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“…On the other hand, the staircase in the papillary muscle of rabbit (290C) was associated with an intensification of the active state (Edman, Grieve & Nilsson, 1966). The shortening in the contraction time during the staircase (Slomic et al 1968) has been claimed to support the assumption that the active state is intensified during the staircase (Desmedt & Hainaut, 1968).…”

Section: Introductionmentioning

confidence: 72%

“…A number ofworkers assumed that potentiation is localized to excitation-contraction coupling (Desmedt & Hainaut, 1968;Close & Hoh, 1968b) and associated with a prolongation of the active state (frog, 00C, Ritchie & Wilkie, 1955). On the other hand, the staircase in the papillary muscle of rabbit (290C) was associated with an intensification of the active state (Edman, Grieve & Nilsson, 1966). The shortening in the contraction time during the staircase (Slomic et al 1968) has been claimed to support the assumption that the active state is intensified during the staircase (Desmedt & Hainaut, 1968).…”

Section: Introductionmentioning

confidence: 99%

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Enhancement and diminution of mechanical tension evoked by staircase and by tetanus in rat muscle

Krarup¹

1981

The Journal of Physiology

147

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SUMMARY1. Potentiation of the isometric twitch tension was compared during and after the staircase and after tetanic stimuli in the fast-twitch extensor digitorum longus muscle of adult Lewis rats at 37-380C.2. With up to 250 stimuli the potentiation rose with an increase in both the frequency and number of stimuli in the staircase (2-5/sec) and the tetanus (100-167/sec). After a tetanus of 375 stimuli (125/sec) the potentiation was smaller.The potentiation 2 sec after a tetanus of250 stimuli (167/sec) was + 132 ± 5% (n = 21, S.E. of mean) which was greater (P < 01001) than at the 250th stimulus at 5/sec, +92+3% (n = 21, S.E. of mean).3. After the staircase the decay of potentiation was initially slow and later more rapid. This was taken to indicate both the recovery ofa process that diminished twitch tension and the decay of a process causing potentiation. After 250 stimuli (5/sec) the rate of decay of the processes causing diminution and potentiation had time constants of 34-5+3-8 sec (n = 18, 5.E. of mean) and 102-2+666 sec (n = 20, S.E. of mean) respectively. Compared with the potentiation, the process causing diminution became relatively more pronounced the greater the frequency of stimuli.4. The decay of post-tetanic potentiation showed an initial rapid and a later slower phase of decay. After a tetanus of 250 stimuli (167/sec) the rates of decay had time constants of 5-7+0 8 sec (n = 16, S.E. of mean) and 113-5+±87 sec (n = 19, S.E. of mean) respectively.5. Compared with the unpotentiated response the time course of the twitch was shortened initially in the staircase and when the post-tetanic potentiation was low. The contraction time was then increasingly prolonged the greater the potentiation and the greater the number of stimuli in the staircase and in the tetanus. The half-relaxation time was the more prolonged the greater the number of stimuli.6. Potentiation can be described in terms of a two-compartment model ofprocesses which show saturation. Both compartments were activated in a tetanus whereas only the compartment with a slow rate of decay was activated in the staircase. It is speculated that the two compartments are related to the excitation-contraction Present address:

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Section: Introductionmentioning

confidence: 72%

Section: Introductionmentioning

confidence: 99%

Enhancement and diminution of mechanical tension evoked by staircase and by tetanus in rat muscle

Krarup¹

1981

The Journal of Physiology

147

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“…The raw data were obtained from the same records used for Table 1. reminiscent of the initiation, though at a later time, of the negative after potential of the normal action potential. The shoulder is clearly displayed in records of 50 and 500 ]/M Zn 2+ spikes reported earlier by our laboratory (Taylor et al, 1972), and it seems detectable in a 5 JIM Zn 2+ record of Edman, Grieve and Nilsson (1966) and in a 100-gM record obtained by Stanfield (1973), but none of these reports made any mention of it. However, a 500-gU record of Mashima and Washio (1964) includes no shoulder.…”

Section: Zinc Mediamentioning

confidence: 83%

Detubulation effects on the action of zinc on frog skeletal muscle action potential

Sandow

Pagala

1978

J. Membrain Biol.

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Detubulation of the untreated fiber decreases the time constant of the action potential's foot (tauf) and increases the maximal rate of rise of the spike (Vmax). Zinc at all concentrations, and regardless of whether the fiber is intact or detubulated, increases tauf and decreases Vmax, and thus seems to decrease Na activation of the fiber. Detubulation was used principally to elucidate the localization and mechanism of the Zn2+-induced retardation of the falling phase of the frog sartorius fiber action potential, which evidently results from a general depression of delayed rectification. At 50 to 1000 mum, Zn2+ not only prolongs repolarization of intact fibers (measured by increase in t0.5, the half-time of the spike's fall), but also produces a marked hump early in this phase. Detubulation of zinc-free fibers reduces t0.5 to about 80% of its intact value, and under Zn2+ treatment t0.5 is increased but only to about 80% of that produced in the inus, detubulation decreases t0.5 in Zn2+-treated fibers not only to about 80% of that produced in the intact fiber, and the falling-phase hump is completely obliterated. Thus, detubulation decreases t0.5 in Zn2+-treated fibers not only by generally eliminating T-tubular participation in action potential generation, but also by subtracting a Zn2+-induced retardation of tubular delayed rectification. Tubular delayed rectification must therefore be an intrinsic feature of normal excitation. These results are further analyzed by means of (i) Stanfield's findings about retardation of delayed rectification by Zn2+ and (ii) Adrian-Peachey's theory of T-tubule participation in action potential generation, which suggests that the Zn2+-evoked repolarization hump signals onset of Zn2+-altered active participation of T-tubules in determining the spike's shape.

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“…of muscle length upon the active state can be adequately controlled, however. Thus, as demonstrated previously (Edman et al 1966, Edman and Nilsson 1968, Brady 1967, it is possible to define the kinetics of the active state in isolated papillary muscles at a constant length of the contractile unit.…”

mentioning

confidence: 79%

“…providing a common parameter for the ability of the muscle to produce tension (PI,,,,) and to shorten actively (VIllils), is applicable in the analysis of the heart muscle function. It was shown that cardiac active state, unlike the situation in the skeletal muscle, has a slow onset and does not reach a plateau during a contraction cycle (also see Brady 1966, Edman, Grieve and Nilsson 1966, Sonnenblick 1966. The analysis furthermore demonstrated that the course of the active state is not definitely programmed when the contraction starts: both the maximal intensity of the active state and the duration of the activity are critically dependent upon the amount of shortening of the contractile uriit during the contraction period, In fact, the intrinsic length changes of the rnizscle 15-10 per cent of the resting muscle length) taking place during a n ordinary isometric contraction are great enough to affect the course of the active state and hence, the isometric twitch output to a substantial degree.…”

mentioning

confidence: 99%

The Dynamics of the Inotropic Change Produced by Altered Pacing of Rabbit Papillary Muscle

Edman

Nilsson

1969

Acta Physiologica Scandinavica

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The time course of the active state, the force‐velocity relationship and the series compliance of rabbit papillary muscles were studied at different inotropic states produced by altered pacing of the muscles within the range 18 to 72 stimulations per minute. The inotropic intervention produced a shift of the force‐velocity curve, without markedly changing the shape of the curve, suggesting that Vmax, the capacity to produce motion, and Pmax the capacity to produce tension, were affected to the same degree. Intensification of the active state in response to an increase in stimulation frequency was associated with a steeper rise of the active state and an earlier attainment of maximum. The series compliance was unaffected by the inotropic intervention. The results are taken as evidence (1) that the two parameters of the active state, Vmax and Pmax, are governed by a common control mechanism in the excitation‐contraction coupling and (2) that the inotropic effect is due to altered kinetics of this control function. The nature of the mechanism governing the active state is discussed in relation to the slicling‐filament theory of muscular contraction.

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Studies of the excitation-contraction mechanism in the skeletal muscle and the myocardium

Cited by 52 publications

References 18 publications

Enhancement and diminution of mechanical tension evoked by staircase and by tetanus in rat muscle

Enhancement and diminution of mechanical tension evoked by staircase and by tetanus in rat muscle

Detubulation effects on the action of zinc on frog skeletal muscle action potential

The Dynamics of the Inotropic Change Produced by Altered Pacing of Rabbit Papillary Muscle

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