Skeletal muscle: from development to function.

Aim of this minireview was to focus attention on some aspects of myogenesis, differentiation and metabolism of muscle in mammals (rodents and humans), and to summarize current knowledge on the issue referring to both our experimental contributions and those of other authors.Particular attention was directed at both the mesodermal stem cells, elements of the early embryonic period, and the regulatory genes. It was also discussed the crucial role of several growth factors, such as myogenin and bFGF, and substances of vital importance to the regulation of contraction: somatomedins [Insulin-like Growth Factors (IGF-I and IGF-II)], interleukin-15 (IL -15), transferrin (Tf), catecholamines (CA). A no secondary role in the metabolism of skeletal muscle is played by serotonin (5-HT) and its precursor [L-tryptophan (L-Tp)]. The presence of L-Tp, in the diet of growing rats, seems to be crucial for protein synthesis and for the increase in the number of mitochondria. It has also highlighted the role played by certain hormones: growth hormone (GH), thyroid hormones (T3 and T4), sex steroids on metabolism, growth and differentiation of skeletal muscle.