Receptor‐controlled Calcium Discharge in Frog Heart Cells

Niedergerke, R.; Page, Sally

doi:10.1113/expphysiol.1989.sp003374

Cited by 10 publications

(6 citation statements)

References 23 publications

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“…The effects of isoprenaline, as well as of variation in [Ca2+]o and stimulation pattern, on all the twitch characteristics, as reported in the present paper, are comparable to those described by previous investigators for multicellular atrial and ventricular preparations from frog heart under similar experimental conditions (Blinks & Koch-Weser, 1963;Chapman & Niedergerke, 1970;Allen & Blinks, 1978;Tung & Morad, 1983;Niedergerke & Page, 1989). In accordance with Tung & Morad (1988), therefore, it can be concluded that the enzymatic isolation procedure does not alter the physiological properties of the myocytes which represent a reliable preparation for the study of myocardial-contraction mechanics.…”

Section: Integrity Of Enzymatically Isolated Myocytessupporting

confidence: 91%

The stimulus interval‐tension relation in enzymatically isolated single myocytes of the frog heart.

Cecchi

Colomo

Poggesi

et al. 1992

The Journal of Physiology

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SUMMARY1. Apparatus for recording the small tensions developed by electrically stimulated single intact myocytes of frog heart is described. A laser-light optoelectronic transducer was used. The compliance of the force probes was 10-20 nm/nN, with a frequency response of 600-900 Hz in Ringer solution. The myocyte shortening during an ordinary twitch contraction was no greater than 1 % of the slack length. The overall sensitivity of the transducer system was 5-10 mV/nN, with a total noise of 0 5-1 nN peak to peak. The experiments were performed at 20-23 'C on either atrial or ventricular myocytes at 2-15-2-2 ,tm sarcomere length, in 1 mM-Ca2± Ringer solution.2. Isoprenaline (5 JIM), increases in external Ca2+ concentration ([Ca2+]0), and shortening of stimulus interval potentiated the myocyte twitch tension. The dependence of twitch characteristics on these inotropic interventions for all the atrial and ventricular myocytes tested was comparable to that of multicellular preparations under similar experimental conditions. This implies that the enzymatic isolation procedure had not altered the physiological properties of the myocytes.3. The stimulus interval-tension relation for premature twitches of atrial and ventricular myocytes showed (i) a very steep rising phase in the region of intervals just longer than 0-52 and 0-66 s (the duration of the mechanical refractoriness in atrial or ventricular cells), (ii) a peak, at intervals of 0*7-48 s, where the twitch tension was strongly potentiated compared to that of the controls, and (iii) as the stimulus interval was further increased, a progressive return to the control level. The stimulus interval-tension relation for steady-state conditions exhibited similar characteristics.4. The degree of tension potentiation by isoprenaline was greater in the controls than in the earliest test twitches. The result was that the stimulus interval-tension relations for isoprenaline-treated myocytes showed a gentler rise and a lower peak than for untreated cells.5. The stimulus interval-tension relation of the heart is a basic property of its cells. It is related to changes in the activation level. The higher the activation level reached in control twitches, the lower the stimulus interval-dependent potentiation capability.

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Section: Integrity Of Enzymatically Isolated Myocytessupporting

confidence: 91%

The stimulus interval‐tension relation in enzymatically isolated single myocytes of the frog heart.

Cecchi

Colomo

Poggesi

et al. 1992

The Journal of Physiology

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“…In frog heart cells ATP or alpha adrenaline action causes additional calcium discharge from the sarcoplasmic reticulam (SR) in association with the action potential (Niedergerke and Page, 1989). In contrast, acetylcholine with G Protein coupled muscarinic (M 2 ) receptor on surface of frog heart muscle cells produces negative inotropic and negative chronotropic effects (Gattuso et al, 1999;Kulkarn, 1999).…”

Section: Samplementioning

confidence: 97%

Evaluation of mechanism for antihypertensive action of Clerodendrum colebrookianum Walp., used by folklore healers in north-east India

Deb¹,

Dutta²

2012

Journal of Ethnopharmacology

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“…Acetaldehyde shortened APD 90 although APD 30 was lengthened. In contrast to acetaldehyde, adrenaline or isoprenaline, which was demonstrated to enhance I Ca , prolonged APD 90 in frog atrial myocytes [18,19]. This suggests different mechanisms of acetaldehyde from those of β-adrenergic agents.…”

Section: Discussionmentioning

confidence: 72%

Effects of Acetaldehyde on Action Potentials and Ca2+ Currents in Single Atrial Myocytes from the Bullfrog

et al. 2012

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Aim: The purpose of the present study was to examine the effects of acetaldehyde on the contractile force and membrane potentials and currents in the bullfrog heart. Methods: Contractile force was recorded using right atrial tissues, and membrane potentials and currents were measured by using whole cell patch clamp methods in right atrial myocytes. Results: Acetaldehyde at 500 µmol/l and 1 mmol/l increased the contractile force significantly. Acetaldehyde at 300 and 500 µmol/l increased the overshoot and the plateau of electrically induced action potentials in a concentration-dependent and reversible manner, while the resting membrane potential did not change. The duration of the action potential (APD₉₀) measured at the 90% repolarization level was shortened. The L-type Ca²⁺ current (I_Ca) increased significantly when 300 and 500 µmol/l were applied. The fast transient inward current, the inward rectifying potassium current and the outward delayed-rectifier potassium current were not changed following acetaldehyde application (500 µmol/l or 1 mmol/l). Conclusion: These results suggest that acetaldehyde increased the I_Ca, thereby increased the contractile force, the overshoot and the plateau of action potentials. The shortening of APD₉₀ may be due to the acceleration of the current decay during the I_Ca inactivation phase.

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Receptor‐controlled Calcium Discharge in Frog Heart Cells

Cited by 10 publications

References 23 publications

The stimulus interval‐tension relation in enzymatically isolated single myocytes of the frog heart.

The stimulus interval‐tension relation in enzymatically isolated single myocytes of the frog heart.

Evaluation of mechanism for antihypertensive action of Clerodendrum colebrookianum Walp., used by folklore healers in north-east India

Effects of Acetaldehyde on Action Potentials and Ca2+ Currents in Single Atrial Myocytes from the Bullfrog

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