Appearance of acetylcholine receptors in cultured myoblasts prior to fusion.

The development of the acetylcholine receptors in chick embryo myoblasts from 11-day old embryos was studied in vitro. Using the purified alpha-bungarotoxin labeled with radioactive iodide, a high concentration of acetylcholine receptors was found in the prefusing myoblasts; most of these receptors were located in the interior of the myoblasts. However, upon the completion of myoblasts fusion, the majority of the acetylcholine receptors appeared on the external cell surface of the myotubes.