Developmental aspects of potassium flux and permeability of the embryonic chick heart
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Published on: May 13, 2016
Insights
Potassium-42 (42K) efflux rates in embryonic chick hearts vary with age, showing minimal efflux in 6-8 day old embryos. External potassium concentration significantly impacts efflux, with permeability increasing with age.
Area of Science:
- * Cardiovascular physiology
- * Developmental biology
- * Ionic transport mechanisms
Background:
- * Understanding ion transport is crucial for cardiac function.
- * Embryonic heart development involves dynamic changes in cellular properties.
- * Potassium (K) and sodium (Na) ion dynamics are fundamental to cardiac electrophysiology.
Purpose of the Study:
- * To investigate age-dependent changes in 42K efflux in embryonic chick hearts.
- * To determine the influence of external K concentration on K efflux across different developmental stages.
- * To correlate ion transport parameters with developmental changes in membrane potential and intracellular ion concentrations.
Main Methods:
- * Measurement of 42K efflux rate coefficient.
- * Determination of transmembrane potential.
- * Quantification of intracellular Na and K concentrations.
- * Stereologic and morphometric analysis of heart volume/surface area.
Main Results:
- * 42K efflux rate coefficient was minimal in 6-8 day old embryos, higher in younger (3-5 days) and older (18-20 days) embryos.
- * External K concentration (Ko) increased 42K efflux five- to sevenfold across all ages.
- * Intracellular K and Na concentrations decreased, while membrane potential increased with age.
- * Potassium permeability (PK) increased with age and decreased significantly in K-free solutions.
Conclusions:
- * Embryonic chick heart 42K efflux is age-dependent, with distinct patterns observed during development.
- * External K concentration is a major regulator of K efflux, independent of extracellular Na except in specific conditions.
- * Developmental changes in heart tissue include altered ion transport and electrophysiological properties, particularly increased K permeability in later stages.
Abstract:
1. The rate coefficient of 42K efflux, the transmembrane potential, the intracellular concentrations of Na and K and the volume/surface area have been measured in embryonic chick hearts of different ages. 2. With respect to age, the rate coefficient for 42K efflux was minimal for preparations from 6-8 day old embryos, and distinctly higher values were obtained for the hearts of 3-5 and 18-20 days. With respect to the effect of external K concentration (Ko), all age groups showed a five- to sevenfold increase in rate coefficient between 2-5 and 140 mM-Ko. The effect of Ko was found to be indepedent of extracellular Na, except in the 18-20 day hearts bathed in K-free solution. 3. Intracellular concentrations of K and Na were found to decrease, membrane potential to increase with age. The volume/surface area measured by stereologic and morphometric techniques did not change with age. 4. The permeability coefficient for K (PK), calculated from the absolute K flux and the measured membrane potentials, was fairly constant for a given age between 2-5 and 20 mM-Ko. In K-free solution, PK was markedly reduced (factor 4). At a given Ko, PK increased twofold between 6-8 and 18-20 days while PNa remained relatively constant.
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