Prostaglandins and cyclic AMP stimulate creatine kinase synthesis but not fusion in cultured embryonic chick muscle cells

Cyclic AMP levels have been measured in cultures derived from 12-day-old chick embryonic muscle. A rise in concentration was found after the onset of myoblast fusion. Cells cultured at a medium Ca²⁺ concentration of 0.1 μM did not fuse and exhibited only a small rise in cyclic AMP concentration during culture. Addition of 1.4 mM Ca²⁺ to these cells after 50 h in culture caused rapid, synchronous fusion with a concomitant rise in cyclic AMP levels. Indomethacin, an inhibitor of prostaglandin synthesis, did not inhibit fusion, but inhibited the rise in cyclic AMP concentration. Indomethacin-treated cultures exhibited lower creatine kinase levels, though no change in the ratio of the three isoenzymes was observed. Addition of prostaglandins E₁ and E₂ to indomethacin-treated cultures overcame this inhibition. We propose that prostaglandin synthesis is a consequence of the stimulation of myoblast fusion and that via cyclic AMP it stimulates protein synthesis.