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Ion levels and membrane potential in chick heart tissue and cultured cells
Insights
During embryonic development, chick heart cells show decreasing intracellular potassium and increasing resting potentials. Cultured heart cells exhibit similar ion concentrations and electrical properties to intact tissue.
Area of Science:
- Developmental biology
- Cardiovascular physiology
- Cellular electrophysiology
Background:
- Understanding ion transport and electrical activity is crucial for studying heart development.
- Chick embryos provide a model for investigating early cardiac electrophysiology.
Purpose of the Study:
- To determine changes in intracellular sodium and potassium concentrations, resting potentials, and overshoots in embryonic chick heart.
- To compare the electrophysiological properties of cultured embryonic chick heart cells with intact tissue.
Main Methods:
- Intracellular ion concentrations were measured using ion-selective electrodes.
- Resting potentials and overshoots were recorded using microelectrodes.
- Comparisons were made between intact heart tissue and cultured heart cells (monolayers and aggregates).
Main Results:
- Intracellular potassium decreased from 167 mM (day 2) to 117-119 mM (days 14-18).
- Intracellular sodium remained stable at 30-35 mM.
- Resting potential increased from -61.8 mV (day 3) to -80 mV (days 14-18).
- Overshoot increased from 12 mV to 30 mV.
- The ratio of sodium to potassium permeability (P(Na)/P(K)) decreased significantly.
- Cultured heart cells showed similar ion concentrations and electrical responses to intact tissue.
Conclusions:
- Embryonic chick heart development (days 2-14) is characterized by declining intracellular potassium and improving electrical properties (resting potential, overshoot).
- Cultured embryonic chick heart cells accurately reflect the electrophysiological characteristics of intact developing heart tissue.
Abstract:
Intracellular concentrations of sodium and potassium as well as resting potentials and overshoots have been determined in heart tissue from chick embryos aged 2-18 days. Intracellular potassium declined from 167 mM at day 2 to 117-119 mM at days 14-18. Intracellular sodium remained nearly constant at 30-35 mM during the same period. The mean resting potential increased from -61.8 mV at day 3 to about -80 mV at days 14-18. The mean overshoot during the same period increased from 12 to 30 mV. P(Na)/P(K) calculated from the ion data and resting potentials declined from 0.08 at day 3 to 0.01 at days 14-18. Thus, the development of embryonic chick heart during days 2-14 is characterized by a declining intracellular potassium concentration and an increasing resting potential and overshoot. Heart cells from 7- to 8-day embryos, cultured either in monolayer or reassociated into aggregates, were compared with intact tissue of the same age. The intracellular concentrations of sodium and potassium were similar in the three preparations and cultured cells responded to incubation in low potassium medium or treatment with ouabain in a manner similar to that of intact tissue. Resting potentials and overshoots were also similar in the three preparations.
