Inotropic effects of different calcium ion concentrations on the embryonic chick ventricle. Comparison of single cultured cells and intact muscle strips

Abstract

The effects of changes in the calcium ion concentration in the medium bathing single beating cultured chick embryo ventricular cells were determined using an electro optical monitoring technique for measuring the amplitude and velocity of cell wall motion. Although single cells showed significant decreases in the amplitude and velocity of cell wall motion during contraction when the calcium ion concentration was lowered from 1.8 mM to 0.9 mM, there were no significant changes in these parameters when the concentration was increased from 1.8 mM to 3.6 mM. Ventricular strips obtained from embryos of the same age showed positive inotropic responses to an increase in the external calcium ion concentration from 1.8 mM to 3.6 mM, and the magnitude of this response increased with increasing embryonic age. These results suggest that there is a reduced positive inotropic responsiveness in young chick embryo ventricular cells, which is particularly marked in the single cultured cell preparation because of the tendency of culturing techniques to select out immature cell populations.