ABSTRACT
Treatment of rat soleus muscles (Kameyama and Etlinger, 1979) or chicken muscle cells (Young et al., 1981) with the Ca2+ ionophore A23187 at low concentration increases the rate of myosin heavy-chain synthesis. The stimulation results from transcription of new myosin heavy-chain mRNA, since it is blocked by actinomycin D (Young et al., 1981). Inhibition of protein synthesis and increased degradation of muscle proteins was observed after treatment with high concentration of Ca2+ ionopheres in chick muscle cultures (Silver and Etlinger, 1985), and in isolated extensor digitorum longus and soleus muscles of the rat (Lewis et al., 1982). The stimulation of protein degradation is mediated by prostaglandin E, but apparently does not involve a calcium-activated protease (Rodemann et al., 1982).
