title: In vitro differentiation of a fast Na+ conductance in embryonic heart cell aggregates.
abstract: 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.
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000367:Age Factors; D000818:Animals; D002454:Cell Differentiation; D002642:Chick Embryo; D046508:Culture Techniques; D003513:Cycloheximide / Q000494:pharmacology; D004553:Electric Conductivity; D006321:Heart / Q000196:embryology* / Q000502:physiology; D009124:Muscle Proteins / Q000096:biosynthesis; D009200:Myocardial Contraction / Q000187:drug effects; D012964:Sodium / Q000502:physiology*; D013779:Tetrodotoxin / Q000494:pharmacology
chemical_list: D009124:Muscle Proteins; D013779:Tetrodotoxin; D003513:Cycloheximide; D012964:Sodium