Recombinant Rat IGF-I/IGF-1 Protein, CF

Insulin-like growth factor I (IGF-I or IGF-1), also known as somatomedin C, is the dominant effector of growth hormone and is structurally homologous to proinsulin. Rat IGF-I/IGF-1 is synthesized as four precursor isoforms with alternate N- and C-terminal propeptides (1). These isoforms are differentially expressed by various tissues (1). The 7.6 kDa mature IGF-I/IGF-1 is identical between isoforms and is generated by proteolytic removal of the N- and C-terminal regions. Mature rat IGF-I/IGF-1 shares 96% and 99% aa sequence identity with human and mouse IGF-I/IGF-1, respectively (2, 3), and exhibits cross-species activity. It shares 61% aa sequence identity with mature rat IGF-II/IGF-2. Circulating IGF-I/IGF-1 is produced by hepatocytes, while local IGF-I/IGF-1 is produced by many other tissues in which it has paracrine effects (1). IGF-I/IGF-1 induces the proliferation, migration, and differentiation of a wide variety of cell types during development and postnatally (4). IGF-I/IGF-1 regulates glucose and fatty acid metabolism, steroid hormone activity, and cartilage and bone metabolism (5 - 8). It plays an important role in muscle regeneration and tumor progression (1, 9). IGF-I/IGF-1 binds IGF-I R, IGF-II R, and the insulin receptor, although its effects are mediated primarily by IGF-I R (10). Heterodimers of insulin receptor/IGF-I R also exist and respond to IGF-I/IGF-1 but not to insulin stimulation (11). IGF-I/IGF-1 association with IGF binding proteins increases its plasma half-life and modulates its interactions with receptors (12).