Animal insulin-like growth factor binding proteins and their biological functions

Insulin-like growth factor (IGF-I, IGF-II) action is influenced by until today known eight forms of insulinlike growth factor binding proteins (IGFBPs). They have been obtained not only from some human and animal tissues and body fluids but also from conditioned medium of cell cultures. An important biological property of the IGFBPs is their ability to increase the circulating half-life of the IGFs. They are able to act as potentiators of cell proliferation. As IGFBPs bind to cell surfaces, they may act either to deliver the IGFs to those surfaces for activation of specific receptors or to activate cell responses independently of receptor activation. Phosphorylation, glycosylation and proteolysis of IGFBPs influence their affinity to IGFs. The IGFBPs in the role of inhibitors may block the activity of the IGFs and be used for antimitogenic therapy. In the last time measuring of IGFBPs levels can be used for diagnosis determination of some endocrine diseases or in differential diagnostics.