Developmental aspects of potassium flux and permeability of the embryonic chick heart.

Carmeliet, Edward; Horres, C. R.; Lieberman, Melvyn; Vereecke, Johan

doi:10.1113/jphysiol.1976.sp011252

Cited by 52 publications

(25 citation statements)

References 31 publications

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“…As noted above, this hyperpolarization is caused by a potassium-induced increase of IK2. The tissue ER with K. = 5 mm is -70 mV (Carmeliet et al 1976), whereas our measurements of ER for Ko = 3-5J mm were in the -80 to -75 mV range. That is, ER displayed a U-shaped dependence on Ko both in whole tissue and in aggregates.…”

Section: Rectification In Embryonic Heart Cellsmentioning

confidence: 55%

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Analysis of subthreshold pace‐maker currents in chick embryonic heart cells.

Clay¹,

Shrier²

1981

The Journal of Physiology

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SUMMARY1. Small re-aggregates of cells dissociated from the ventricles of 7-day-old chick embryonic hearts beat spontaneously in low external potassium concentration (K0 = 1-3 mM) tissue culture medium. This activity was blocked by the addition of tetrodotoxin (TTX) or potassium ions to the external medium.2. A two-micro-electrode voltage-clamp technique was used to analyse the subthreshold currents responsible for the pace-maker depolarization.3. Voltage-clamp steps 6-10 see in duration revealed a time-dependent current having first order kinetics. Its membrane potential range of steady-state activation was -90 to -60 mV.4. The current kinetics were qualitatively similar to those of Hodgkin & Huxley (1952b) with a peak time constant of approximately 1 see at V =-75 mV. The kinetics were independent of K0.5. The time-dependent current was attributed to gated membrane channels. The fully activated current-voltage (I-V) relation of the channels was determined from the ratio of the amplitudes of the time-dependent currents during and after voltage-clamp steps following the procedure of Noble & Tsien (1968).6. The fully activated I-V relation displayed inward rectification with negative slope conductance at potentials more than 15 mV positive to its reversal potential.Changes of Ko shifted the I-V curve along the voltage axis like a potassium electrode.7. The time-independent (background) current was obtained by subtracting the gated channel current from the steady-state I-V curve. This current also rectified in the inward direction.8. The inwardly rectifying I-V relations were theoretically described by a channel having a row of ion-selective sites along which ions move in a single file (Hodgkin & Keynes, 1955), and a membrane-bound particle which blocked the channel in a voltage-dependent manner.9. The relationship ofthe voltage-clamp results to spontaneous activity is discussed and comparisons are made with measurements from whole embryonic heart and other cardiac tissues.

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Section: Rectification In Embryonic Heart Cellsmentioning

confidence: 55%

“…For example, Carmeliet et al (1976) found that the labelled potassium efflux at KO = 2-5 mm was twice as large as that at KO = 0. As noted above, this increase of Ko hyperpolarizes ER, and it also depolarizes EK.…”

Section: Rectification In Embryonic Heart Cellsmentioning

confidence: 99%

Analysis of subthreshold pace‐maker currents in chick embryonic heart cells.

Clay¹,

Shrier²

1981

The Journal of Physiology

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show abstract

“…be in error or the apparent intracellular activity coefficients must change dramatically during development. For example, we can use the concentration measurements of Carmeliet et al (1976) for calculation of apparent activity coefficients. McDonald & DeHaan (1973) for 4 and 18 day hearts yJ is 0-46 and 0-76 and yia is 0-36 and 0'20 respectively.…”

Section: Discussionmentioning

confidence: 99%

“…The Ki efflux studies of Carmeliet et al (1976) indicated a twofold increase in PK between 6-8 days and [18][19][20] days. This agrees with our 584 K1 AND Nai ACTIVITIES IN EMBRYO HEART calculation of a twofold decrease in PN/PK in this period.…”

Section: Discussionmentioning

confidence: 99%

“…However, studies of developmental changes in Vm and intracellular ionic concentrations in the chick embryo heart are in conflict with this view. A progressive hyperpolarization occurs with maturation from day 2 to day 21 (hatching), but chemical analysis has shown a fall in cellular K. For example, Carmeliet, Horres, Lieberman & Vereecke (1976) reported that intracellular K concentration ([K+]1) decreases from 151 to 122 mM with maturation, in the face of a hyperpolarization of 7 mV, while intracellular Na concentration ([Na+li) stays nearly constant at 15 mM.…”

Section: Introductionmentioning

confidence: 99%

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Intracellular potassium and sodium activities of chick ventricular muscle during embryonic development.

Fozzard¹,

Sheu²

1980

The Journal of Physiology

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SUMMARY1. The basis of the resting potential of chick embryo ventricular muscle was studied by use of ion-selective micro-electrodes. Membrane resting potential hyperpolarized from -65-4 + 1-1 mV (mean + s.E.) at age 4 day to ---75-8 + 0-6 mV at age 18 day. Action potential overshoot increased from + 19-8 + 0-9 at age 4 day to +33-1+0-6mVatage 18 day.2., Intracellular K+ activity measured with ion-selective micro-electrodes increased from 71-3 + 1-9 mm at age 4 day to 89-9 + 1-1 mM at age 18 day. Intracellular Na+ activity decreased from 12-5 + 0-4 to 7-0 + 0-3 mm during the same period. The difference between membrane resting potential and the calculated potassium equilibrium potential decreased with development. PNa/PK estimated from the constant field equation decreased from 0-012 at age 4 day to 0-005 at age 18 day.3. The hyperpolarization of resting potential and the increased action potential overshoot during development could be explained by a rise in intracellular K+ activity and a fall in intracellular Na+ activity, as if the Na-K exchange pump became more active.

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Effects of 2.45‐GHz microwave radiation on embryonic quail hearts

Galvin

McRee

Lieberman

1980

Bioelectromagnetics

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Although exposure to nonionizing electromagnetic radiation has been reported to cause a variety of systemic alterations during embryonic development, there are few reports of the induction of specific physiology or morphologic changes in the myocardium. This study was designed to examine the effects of microwave radiation on cardiogenesis in Japanese quail embryos exposed during the first eight days of development to 2.45-GHz continuous-wave microwaves at power densities of 5 or 20 mW/cm2. The specific absorption rates were 4.0 and 16.2 mW/g, respectively. The ambient temperature for each exposure was set to maintain the embryonated eggs at 37.5 degree C. This did not preclude thermal gradients in the irradiated embryos since microwaves may not uniformly absorbed. The test exposure levels did not induce changes in either the morphology of the embryonic heart or the ultrastructure of the myocardial cells. Analysis of the enzymatic activities of lactate dehydrogenase, glutamic oxaloacetic transaminase, and creatine phosphokinase failed to reveal any statistically significant differences between the nonexposed controls and those groups exposed to either 5 or 20 mW/cm2. The data indicate that 2.45-GHz microwave radiation at 5 or 20 mW/cm2 has no effect on the measured variables of the Japanese quail myocardium exposed during the first eight days of development.

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Developmental aspects of potassium flux and permeability of the embryonic chick heart.

Cited by 52 publications

References 31 publications

Analysis of subthreshold pace‐maker currents in chick embryonic heart cells.

Analysis of subthreshold pace‐maker currents in chick embryonic heart cells.

Intracellular potassium and sodium activities of chick ventricular muscle during embryonic development.

Effects of 2.45‐GHz microwave radiation on embryonic quail hearts

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