PROOPIOMELANOCORTIN NEUROPEPTIDE RECEPTORS ON DEVELOPING AND DYSTROPHIC MUSCLE-FIBERS

Autoradiography was used to investigate the presence of corticotropin and beta-endorphin receptors on soleus extensor digitorum longus, and diaphragm muscles of normal and dystrophic adult mice and developing mice. In both adult and developing mice, specific binding sites for both [I-125]ACTH and [I-125]beta-endorphin were present in some fibers in all of the muscles examined. The specific binding sites appeared to be distributed over the length of the surface membrane in the fibers that expressed them. There were significantly higher proportions of fibers exhibiting the specific beta-endorphin and the specific ACTH binding sites in the three muscle types in mice of 5 d of age compared to the muscles of the normal adult. There was also a higher proportion of fibers with the putative ACTH and beta-endorphin receptors in the three muscle types in dystrophic mice.