Open AccessThe Ionic Basis of Electrical Activity in Embryonic Cardiac Muscle
Author(s) -
Billy K. Yeh,
B F Hoffman
Publication year - 1968
Publication title -
the journal of general physiology/the journal of general physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.064
H-Index - 127
eISSN - 1540-7748
pISSN - 0022-1295
DOI - 10.1085/jgp.52.3.666
Subject(s) - extracellular , embryonic heart , resting potential , potassium , sodium , intracellular , embryonic stem cell , biophysics , extracellular fluid , hatching , cardiac muscle , electrophysiology , chemistry , membrane potential , medicine , anatomy , endocrinology , biology , biochemistry , zoology , organic chemistry , gene
The intracellular sodium concentration reported for young, embryonic chick hearts is extremely high and decreases progressively throughout the embryonic period, reaching a value of 43 mM immediately before hatching. This observation suggested that the ionic basis for excitation in embryonic chick heart may differ from that responsible for electrical activity of the adult organ. This hypothesis was tested by recording transmembrane resting and action potentials on hearts isolated from 6-day and 19-day chick embryos and varying the extracellular sodium and potassium concentrations. The results show that for both young and old embryonic cardiac cells the resting potential depends primarily on the extracellular potassium concentration and the amplitude and rate of rise of the action potential depend primarily on the extracellular sodium concentration.