Staircase in frog ventricular muscle. Its dependence on membrane excitation and extracellular ionic composition.

Chesnais, J. M.; Kavaler, Frederic; Anderson, Thomas W.; Coraboeuf, E

doi:10.1161/01.res.43.6.917

Cited by 7 publications

(2 citation statements)

References 25 publications

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“…For instance, movements of Ca 2+ across the sarcolemma through Na+-Ca2+ exchange and "Na+ pump lag" (Lado et al ., 1982;Langer, 1983) participate in the long-term changes of tension amplitude of the positive staircase, which takes place over more contractions in intact than in skinned cardiac cells. Frequency-dependent changes in the duration of the action potential plateau (Boyett and Jewell, 1980) might also play a role in the positive staircase in the frog ventricle (Chesnais et al, 1978), where the SR seems to play no role in beat-to-beat Ca" release and accumulation (Fabiato, 1983 ; but see Winegrad, 1979). There is redundancy in the control of cardiac excitationcontraction coupling.…”

Section: Discussionmentioning

confidence: 99%

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Simulated calcium current can both cause calcium loading in and trigger calcium release from the sarcoplasmic reticulum of a skinned canine cardiac Purkinje cell.

Fabiato¹

1985

The Journal of General Physiology

429

202

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Skinned canine cardiac Purkinje cells were stimulated by regularly repeated microinjection-aspiration sequences that were programmed to simulate the fast initial component of the transsarcolemmal Ca from the sarcoplasmic reticulum (SR) . The simulated slow component did not affect the tension transient during which it was first introduced but it potentiated the subsequent transients . The potentiation was not observed when the SR function had been destroyed by detergent. The potentiation decreased progressively when the slow component was separated by an increasing time interval from the fast component. The potentiation was progressive over several beats under conditions that decreased the rate of Ca" accumulation into the SR (deletion of calmodulin from the solutions; a decrease of the temperature from 22 to 12°C). In the presence of a slow component, an increase of frequency caused a positive staircase, and the introduction of an extrasystole caused a postextrasystolic potentiation . There was a negative staircase and no postextrasystolic potentiation in the absence of a slow component. These results can be explained by a time-and Ca 2 '-dependent functional separation of the release and accumulation processes of the SR, rather than by Ca 21 circulation between anatomically distinct loading and release compartments. The fast initial component of transsarcolemmal Ca 21 current would trigger Ca 2' release, whereas the slow component would load the SR with an amount of Ca2' available for release during the subsequent tension transients .

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Section: Discussionmentioning

confidence: 99%

“…A. FABIATO Stimulation of a Skinned Cardiac Cell by Simulated Ca a+ Current 31 7 staircase in the frog ventricle (Chesnais et al, 1978), where the SR seems to play no role in beat-to-beat Ca" release and accumulation (Fabiato, 1983 ; but see Winegrad, 1979). There is redundancy in the control of cardiac excitationcontraction coupling.…”

mentioning

confidence: 99%

Simulated calcium current can both cause calcium loading in and trigger calcium release from the sarcoplasmic reticulum of a skinned canine cardiac Purkinje cell.

Fabiato¹

1985

The Journal of General Physiology

429

202

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Force frequency relation in the myocardium of rainbow trout

Hove‐Madsen

Gesser

1989

J Comp Physiol B

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Isolated heart ventricular preparations from rainbow trout were electrically stimulated to contraction. Following a temporary change in stimulation rate from 0.2 Hz to a higher value, the force fell to a minimum after which it increased and levelled off. Upon the return to 0.2 Hz a further transient increase in force appeared. The latter two responses were stimulated by an increased extracellular K+, which is known to inactivate the Na+ channel. The initial negative inotropic effect, in contrast to the two subsequent positive effects, was associated with a parallel decrease in amplitude of the action potential measured in 15 mM K+, used as an index of the Ca2+ influx. One micromolar (1 microM) ryanodine did not affect either the negative or the positive responses due to an increase in stimulation rate, but depressed the force developed after prolonged periods of rest. Ten micromolar (10 microM) adrenaline strongly inhibited the positive effects of an elevation of frequency. An elevation of extracellular Na+ from 141 to 166 mM had a similar effect. In conclusion, the positive effects occurring in 15 mM K+ do not seem to depend on the initial Na+ current. They may nevertheless depend on changes of the cellular Na+ balance as suggested by the effects of adrenaline, K+ and Na+. The functional role of the sarcoplasmic reticulum is unclear.

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The ‘sodium pump lag’ revisited

Langer

1983

Journal of Molecular and Cellular Cardiology

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Staircase in frog ventricular muscle. Its dependence on membrane excitation and extracellular ionic composition.

Cited by 7 publications

References 25 publications

Simulated calcium current can both cause calcium loading in and trigger calcium release from the sarcoplasmic reticulum of a skinned canine cardiac Purkinje cell.

Simulated calcium current can both cause calcium loading in and trigger calcium release from the sarcoplasmic reticulum of a skinned canine cardiac Purkinje cell.

Force frequency relation in the myocardium of rainbow trout

The ‘sodium pump lag’ revisited

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