Embryonic chick cardiac myocytes can differentiate fast Na+ conductance channels in vitro, a process dependent on active protein synthesis.
Supports mechanistic studies of cardiac myocyte maturation in vitro; leaves open relevance to mammalian or human electrophysiology.
Aggregates of 3-day chick cardiac myocytes, after 2 days of gyration culture, lack a tetrodotoxin-sensitive, fast Na+ conductance. After 2--3 additional days in vitro these aggregates were shown by three different criteria to have developed such a conductance mechanism: (a) action potential upstroke velocities greater than 90 V/sec; (b) suppression of spontaneous activity by tetrodotoxin; and (c) presence of a fast component of inward current recorded during voltage clamp. These membrane properties were similar to those of aggregates derived from 7-day hearts that had developed in ovo. The differentiation of fast Na+ conductance channels was a dependent upon active protein synthesis but not upon the presence of exogenous macromolecules.
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Nathan et al. (1978) studied this question.
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