Early presence of phospholamban in developing chick heart

Abstract

Phosphorylation of phospholamban and development of reticular Ca²⁺ transport were studied in crude membrane preparations of embryonic, newborn and adult chick heart. Maximal phosphorylation of phospholamban by added catalytic subunit of cyclic AMP‐dependent protein kinase increases from embryonic day 4–15. It decreases with further development. In the same membrane preparations active Ca²⁺‐uptake into vesicles of sarcoplasmic reticulum rises from day 4–7 and decreases then slightly until day 20. A several‐fold increase in Ca²⁺‐transport activity occurs at the time of hatching. The data indicate separate genetic control for synthesis of phospholamban and sarcoplasmic reticulum Ca²⁺‐ATPase.