Electrical Properties of Embryonic Heart Cells

Sperelakis, Nick

doi:10.1016/b978-0-12-208950-3.50008-9

Cited by 44 publications

(31 citation statements)

References 149 publications

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“…The rhythmic spontaneous action currents of the 4-day heart, for example, are carried primarily via a "slow" sodium conductance (Sperelakis, 1972). Later in development, membrane selectivity changes to involve a fast sodium-specific mechanism .…”

Section: Introductionmentioning

confidence: 99%

Ultraviolet-induced alterations of beat rate and electrical properties of embryonic chick heart cell aggregates.

Nathan¹,

Pooler²,

DeHaan³

1976

The Journal of General Physiology

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A B S T R A C T Embryonic heart cell aggregates were irradiated with ultraviolet light at wavelengths between 260 and 310 nm. Spontaneous beat rate was monitored with the aid of a closed-circuit TV camera and, in separate experiments, electrophysiological changes were assayed by intracellular recording. The characteristic response of 7-day aggregates was an increase in spontaneous beat rate to a maximum plateau level, followed by a rather abrupt cessation of beating. Intracellular recordings during irradiation showed a marked decline in the maximum rate of rise, overshoot, and repolarization phase of the action potential, and a significant change in threshold toward zero. The action spectrum for the termination of beating peaked between 290 and 295 nm; it fell off sharply at longer wavelengths and more slowly at shorter wavelengths. The maximum increase in beat rate was increasingly greater for shorter wavelengths and exhibited no peak in the wavelength range investigated. The sensitivity of aggregates to 295-nm light, as measured by the inverse of irradiation time required to terminate beating, decreased with increasing aggregate size and external potassium concentration, was relatively independent of temperature, and increased with embryonic age. The ultraviolet-induced increase in beat rate and termination of beating are attributed to separate complementary processes, a depolarization of the membrane, and a decline in "fast" sodium conductance.

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Section: Introductionmentioning

confidence: 99%

Ultraviolet-induced alterations of beat rate and electrical properties of embryonic chick heart cell aggregates.

Nathan¹,

Pooler²,

DeHaan³

1976

The Journal of General Physiology

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“…The decrease of the spontaneous rate was already described by LEHMKUHL (1965) andSACHS (1975). In TTX medium, the fast Na + channel must have been blocked and the inward current would be carried through Cat + and slow Na + channels (SPERELAKIS, 1972;KOJIMA and SPERELAKIS, 1983). MACKENZIE and STANDEN (1982) have shown that the peak action potential was increased by prolongation of the stimulation interval because of the slow recovery from inactivation of K+ outward current.…”

Section: Discussionmentioning

confidence: 99%

Relationship between contraction strength and stimulation frequency in cultured chick embryonic heart cells.

Toyota¹,

Matsumura²

1989

Jpn.J.Physiol

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Membrane potential and contraction were investigated in cultured chick embryonic heart cell aggregate. The cells were stimulated through the intracellular microelectrode, and the contraction of the cell aggregate was measured from the shortening of the diameter. The contraction decreased if the stimulation frequency was raised in the range between 20/min and 100/min; namely, the negative relationship between contraction strength and stimulation frequency. The peak action potential or plateau duration was not affected by the change in the stimulation frequencies unless they exceeded 60/min, but they were shortened at frequencies higher than 75/min. In the latter case, the decrease of contration strength was related to the shortening of plateau duration. If the stimulation frequency was lowered suddenly, the following contraction was transiently increased without any noticeable change in the shape of the action potential. When TTX was added (3-10 x 10-6M) , the rate of the spontaneous activity was reduced, which made it possible to study the contraction strength at low stimulation frequencies. In TTX medium, similar to the observations in the control medium, the relationship between contraction strength and stimulation frequency was also negative. In the medium containing TTX plus verapamil (5-9 x 10-' M), the peak action potential was inhibited during the repetitive stimulation dependently on the stimulation frequency, accompanied by the concomitant decrease of contraction strength. These results suggest that the negative inotropic effect of the stimulation frequency is caused in part by the change in Ca2+ inflow.

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“…We have found that the coronary bed contains blood which contains K+, even though we intermittently flushed the heart with K'-free solution [19], as K+ moves from the intracellular to the extracellular space. Our observations suggest that even when we use a K'-free solution, the extracellular K+ concentration does not fall to zero and averaged about 5 mmol.…”

Section: Discussionmentioning

confidence: 99%

The use of a nondepolarizing cardioplegic solution for cardiac preservation has a beneficial effect on the left ventricular diastolic function

Sunamori¹,

Shimizu²,

Tabuchi³

et al. 2001

Transplant Int

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We have developed a nondepolarizing solution (NDS) that retards myocardial calcium accumulation during cardioplegia. This study compares 1) the membrane resting potential (Em) in Purkinje fibers during cardioplegia induced by NDS or University of Wisconsin solution (UW) at normothermia and hypothermia for 6 h, 2) left ventricular (LV) diastolic function of isolated canine hearts preserved with NDS or UW for 6-and 12 h in hypothermia to elucidate the relationship between diastolic function and myocyte physiology (n = 8, each group), and 3 ) the effect of Non-depolarizing solution (NDS) compared with Bretschneider's HTK solution on LV diastolic function in isolated rabbit hearts using the Langendorff model in normothermia (n = 10, each group). The membrane resting potential (Em) was as follows: NDS in normothermia, -71 mV (2 min), -65 mV (30 min), and -52 mV (60 min); NDS in hypothermia, -40 mV (1 h) and -32 mV (6 h), while UW in hypothermia 0 mV (6 h). Myocardial calcium accumulation during reperfusion in the NDS groups was minimal and significantly lower than in the UW groups after the 6-and 12 h preservations. Postreperfusion myocardial cyclic adenosin monophosphate (CAMP) and adenosin triphosphate (ATP) concentrations in the NDS groups were closer to normal than in the UW groups after the 6-and 12 h preservations. The postreperfusion myocardial Ca concentration correlated with the cAMP ( r = -0.68, n = 25, P = 0003) and cyclic guanosine monophosphate (cGMP) concentrations ( I = -0.69, n = 25, P = 0.003). The left ventricular end-diastolic pressure (LVEDP) after reperfusion correlated with myocardial ATP (r = -0.65, n = 25, P = 0.003) and Ca concentrations ever, the parameter indicating LV elasticity (max LV -dp/dt) correlated with neither the Ca or ATP concentration following reperfusion. NDS prevented stiffness (increased LVEDP) better than HTK during normethermic cardioplegia for 30 min. These results in vitro suggest that NDS prevents myocardial Ca accumulation, depletion of ATP and CAMP, and preserves LV diastolic function, particularly stiffness after reperfusion, for up to 12 h. Furthermore, the mycoardial Ca concentration is inversely correlated with the cAMP and cGMP concentrations.(r = -0.68, = 25, P = 0005). HOW-

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Electrical Properties of Embryonic Heart Cells

Cited by 44 publications

References 149 publications

Ultraviolet-induced alterations of beat rate and electrical properties of embryonic chick heart cell aggregates.

Ultraviolet-induced alterations of beat rate and electrical properties of embryonic chick heart cell aggregates.

Relationship between contraction strength and stimulation frequency in cultured chick embryonic heart cells.

The use of a nondepolarizing cardioplegic solution for cardiac preservation has a beneficial effect on the left ventricular diastolic function

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