ABSTRACT
The intermixing of chick embryonic heart ventricle cells was studied in cellular aggregates as a function of embryonic age of the cells. Cell mobility, as measured by intermixing of radiolabelled and unlabelled cells, was high in cells derived from young embryos: 5.36 ± 1.05 cell diameters per 2.5 days for 6-day-old heart ventricle cells. During development, mobility steadily declined to 1.56 ±0 24 cell diameters per 2.5 days for 18-day old cells. Treatment of aggregates with 1.0 mM theophylline plus 1.2 mM dibutyryl cyclic AMP resulted in greatly decreased mobility, particularly in aggregates of the more mobile younger cells. Depending on the embryonic age of the heart ventricle cells, this treatment reduced mobility by 45.3 to 89.4%. These data are consistent with an age-dependent decrease in intrinsic mobility superimposed upon a contact-paralysis mediated inhibition of movement present in solid tissues. In addition, the sensitivity of heart ventricle cells to inhibition by agents that increase intracellular cyclic AMP levels suggest that this is another possible inhibitory mechanism, although its physiological significance has not been established.
