Effect of insulin-like growth factor-1 (IGF-1) on muscle and bone growth in experimental models.

The effect of protein restriction on the growth of muscle, bone and body tissue of rats fed a diet containing 5% protein (experimental group) and 12% protein (control group) was studied. The following parameters were analyzed: body, muscle and cartilage growth, tibial length, plasma insulin IGF-1 concentrations, and tissue proteoglycan, protein, RNA and insulin-like growth factor-1 concentrations. Protein synthesis in tissues was also determined. Except for protein concentration in the two tissues and of insulin-like growth factor-1 in cartilage, all other values differed significantly between groups. The lower ration and protein ingestion by group 1 receiving a 5% case in diet provoked a reduced secretion of the anabolic hormones insulin and IGF-1 and a lower synthesis of proteoglycans, RNA and protein, impairing total body growth and growth of the tissues analyzed.