TRANSMEMBRANE POTENTIALS OF TRYPSIN-DISPERSED CHICK HEART CELLS CULTURED IN VITRO.

Abstract

Hearts (ventricles) from 6- to 8-day-old chick embryos were cultured 1–7 days. Single cells reassembled into various communities of cells which usually contracted synchronously. Many cells were spontaneously active; quiescent cells could be driven. The average magnitude of the action potentials after microelectrode sealing was 71.2 ± 1.5 mv (range of 40–108 mv) and that of the resting potentials 59.0 ± 1.2 mv (range of 40–84 mv). Maximum velocity of depolarization varied between 1–5 v/sec and positive afterpotentials of 6–10 mv were often found. The duration of the action potential varied between 150–500 msec. Plateaus were observed in only a few of the cells; often a second component appeared on the repolarization phase of the spike. Many cells had pacemaker potentials of about 10 mv. However, even though pacemaker potentials were present, many cells were fired by transmission of excitation from neighboring cells; in such cases, a prepotential was generally observed as a step in the rising phase of the action potential. The data from trypsin-dispersed cells were compared with those of nondispersed clumps and with noncultured intact embryonic hearts. The results indicate that the electrophysiological properties of trypsin-dispersed cultured myocardial cells are similar to those of cells in intact embryonic or adult hearts.