APPEARANCE OF ACETYLCHOLINE RECEPTOR IN DIFFERENTIATING CULTURES OF EMBRYONIC CHICK BREAST MUSCLE

Abstract

It is now well established that primary cultures of embryonic muscle tissue (1, 2) and muscle cell lines (2, 3) elaborate acetylcholine receptor during the process of muscle formation . However, the precise timing of the appearance of receptor with regard to the cessation of DNA synthesis, cell fusion, and the synthesis of the cytoplasmic and contractile proteins, major events that mark the course of muscle differentiation, has yet to be elucidated . Previous studies (1-3) have been hampered by the lack of rapid fusion kinetics . We have measured the appearance of acetylcholine receptor in rapidly differentiating cultures of embryonic chick skeletal muscle, under normal and fusion-arrested conditions (4-6), using iodine125labeled neurotoxins from elapid snake venoms as specific markers (8) . This method has been used to assay receptor in adult muscle (9-11), electrogenic tissue (12), and cultures of embryonic muscle (1-3) . This paper demonstrates that the elaboration of receptor in differentiating muscle, unlike other muscle proteins which have been previously assayed during differentiation (4-7), is not dependent upon the fusion process and can proceed in the absence of fiber formation .