Veratridine stimulation of calcium uptake by chick embryonic heart cells in culture.

Veratridine (2 X 10(-5) to 1 X 10(-4)M) stimulated Ca uptake into monolayer cultures of chick embryonic heart cells in a dose-dependent manner. The stimulation of veratridine was independent of the age of the chick embryos from which the heart cells were taken, and was inhibited by tetrodotoxin (3 microM). The half-maximal effect of veratridine was 37 microM. Since young embryonic hearts have few or no functional fast Na channels (Sperelakis, N. (1981) Cardiac Toxicol 1, 39-108), the present results indicate that the action of veratridine is not dependent solely on fast Na channels, but could be related to other properties of the surface membrane, such as increasing the resting Na permeability and/or opening of the slow Na channels. The increased Ca influx could then be a consequence of the Ca0:Nai exchange reaction.