Activity levels of calcium/phospholipid-dependent protein kinase were examined in preparations of atria and ventricles from embryonic chick hearts at various stages of development. Activity of protein kinase C was much higher in atria than ventricles. Protein kinase C activity underwent a progressive increase in atria during cardiogenesis, being highest just prior to hatching, followed by a profound decrease in activity after hatching. In contrast, activity of cyclic AMP-dependent protein kinase (protein kinase A), while also higher in atria than ventricles, remained relatively constant at the developmental stages examined, likewise decreasing following hatching. These progressive changes in atrial protein kinase C activity suggest a potential regulatory role for this enzyme in cardiogenesis.
Animals Chick Embryo