Slow Ca2+ and Na+ responses induced by isoproterenol and methylxanthines in isolated perfused guinea pig hearts exposed to elevated K+

Schneider, Joel A.; Sperelakis, Nick

doi:10.1016/0022-2828(75)90084-x

Cited by 165 publications

(37 citation statements)

References 45 publications

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“…The muscles were driven electrically by square wave pulses of 6 msec duration and a voltage about 2-fold threshold at a frequency of 0.1 Hz. When the membrane potential was clamped, the potential was usually held at the gap resting potential and SPERELAKIS, 1975;GOTO et al, 1976GOTO et al, , 1977 Our present results, however, appeared rather inconsistent with those reports, since ATP and GTP showed the positive inotropic effect which was unaffected by the presence of propranolol. This discrepancy could be due primarily to the difference of species, mammalian and amphibian, and secondarily to that of the experimental conditions.…”

Section: Methodscontrasting

confidence: 97%

Nature of Catecholamine-like Actions of ATP and Other Energy Rich Nucleotides on the Bullfrog Atrial Muscle

1978

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Section: Methodscontrasting

confidence: 97%

Nature of Catecholamine-like Actions of ATP and Other Energy Rich Nucleotides on the Bullfrog Atrial Muscle

1978

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“…It has been suggested that the cardiac action potential is dependent on the intracellular levels of cyclic AMP and ATP (Carmeliet, 1978;Schneider & Sperelakis, 1975). Actually, without these substances in the internal solution, the action potential became gradually smaller.…”

Section: Effects Of Various Internally Applied Substances On Action Pmentioning

confidence: 99%

Modulation by intracellular ATP and cyclic AMP of the slow inward current in isolated single ventricular cells of the guinea‐pig.

Irisawa¹,

Kokubun²

1983

The Journal of Physiology

159

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and -40 mV, the slow inward current (isi) was activated at potentials positive to -20 mV. The inactivation time course of isi was fitted by two exponential components in the potential range between -10 mV and + 30 mV.4. By increasing ATP from 2 to 9-5 mm in the solution, the amplitude of i5i was increased and the slow component of inactivation was accelerated. The steady-state current-voltage relationship (I-V curve), exhibited a negative slope that became steeper after increasing the ATP concentration. The current was shifted towards the outward direction between -40 mV and -10 mV and became more inward between -10mV and +40mV.

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“…5A and 6B). Caffeine inhibits the activity of phosphodiesterase, increases intracellular cyclic AMP, and enhances the Ca current through the slow channel (SCHNEIDER and SPERELAKIS, 1975;YATANI et al, 1984). Ryanodine which has no direct effect on the Ica (SUTKO and KENYON,1983) failed to exert such effects (Figs.…”

Section: Discussionmentioning

confidence: 99%

Two differential mechanisms of automaticity in diseased human atrial fibers.

et al. 1988

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The ionic mechanisms of automaticity in spontaneously active preparations (n = 38) from "diseased" human atria were investigated. The cycle length (CL) of the automatic action potential (AAP) ranged from 0.6 to 4.5 s (mean + S.D.: 2.0 + 1.0 s). The AAP from preparations obtained from non-digitalized patients (group 1, n = 29) showed various CLs, in that 16 patients had a CL longer than 2.0 s (slow-type AAP) while in tissues from the other 13 patients, the CL was 2.0 s or less (fast-type AAP). On the other hand, all preparations obtained from the digitalized patients prior to cardiac surgery (group 2, n = 9) had the fast-type AAP (CL <_ 2.0 s). The slow-type AAP was accelerated and changed to the fast one after application of ouabain (1 µM) or by perfusing with 50% [Na + ]o Tyrode solution. Ryanodine (1 tiM), a specific inhibitor of calcium release from the sarcoplasmic reticulum (SR), markedly lengthened the CL of fast-type AAP, without affecting the slow-type AAP. In contrast, caffeine (15 mM) shortened the CL of the slow-type AAP and remarkably lengthened the CL of the fast-type AAP, as is the case in ryanodine. The rate of slow-type AAP was enhanced with an increase in [Ca2+]o and depressed with a decrease in [Ca2 +]o or with application of diltiazem, a Ca2 + channel blocker. The slow-type AAP was changed to the fast-type AAP by stretching the preparation by about 20%. In vitro preparations excised from patients with dilated atria revealed a shorter CL of AAPs. We conclude that in "diseased" human atrial preparations, the ionic mechanism responsible for generation of slow-and fast-type automaticity differs. Slow automaticity (CL >2.0 s) perhaps relates to activation of the slow inward Ca2 + current, while the fast-type automaticity (CL <2.0 s) is linked to cyclic increases in [Ca2 +]~.

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Slow Ca2+ and Na+ responses induced by isoproterenol and methylxanthines in isolated perfused guinea pig hearts exposed to elevated K+

Cited by 165 publications

References 45 publications

Nature of Catecholamine-like Actions of ATP and Other Energy Rich Nucleotides on the Bullfrog Atrial Muscle

Nature of Catecholamine-like Actions of ATP and Other Energy Rich Nucleotides on the Bullfrog Atrial Muscle

Modulation by intracellular ATP and cyclic AMP of the slow inward current in isolated single ventricular cells of the guinea‐pig.

Two differential mechanisms of automaticity in diseased human atrial fibers.

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