Enhanced potency of truncated insulin-like growth factor-I (des(1-3)IGF-I) relative to IGF-I in lit/lit mice.

The relative potencies of insulin-like growth factor (IGF-I) and the N-terminal truncated derivative, des(1-3)IGF-I, have been compared in lit/lit mice. Injection of 30 micrograms IGF-I, 30 micrograms des(1-3)IGF-I or 3 micrograms des(1-3)IGF-I daily for 3 weeks increased total length and nose-rump length of the animals substantially more than in controls or animals treated with 3 micrograms IGF-I daily. Body weight changes were not statistically significant. The lower dose of des(1-3)IGF-I, but not that of IGF-I, led to increases in kidney and heart weights relative to controls, while the higher dose of either IGF-I or des(1-3)IGF-I also increased the weights of liver, lungs and stomach. These results indicate that the higher potency of des(1-3)IGF-I demonstrated in cultured cells also applies in vivo to at least one strain of GH-deficient animals.