Biosynthetic somatomedin C (SM-C/IGF-I) increases the length and weight of Snell dwarf mice.

An Escherichia coli derived somatomedin-C/IGF-I preparation (rec-IGF-I) with an amino acid sequence identical to the natural IGF-I derived from human plasma, increases body length and weight, as well as the growth of several organs of Snell dwarf mice, when administered for 4 wk. After 2 wk of treatment rec-IGF-I (22.2 micrograms/day) induced a significant increase over buffer treated controls, to a comparable degree as obtained with bacterially synthesized human growth hormone (bhGH; 8.4 micrograms/day). The weight/length ratio of rec-IGF-I and bhGH-treated dwarf mice after 4 wk of treatment were not significantly different. A significant increase over controls was obtained with both preparations. Organs with increased weights after bhGH treatment (brain; submandibular salivary glands; heart, liver, kidneys, thymus, and spleen) were also heavier after rec-IGF-I. Significance was only reached for the kidneys and the spleen and the musculus quadriceps femoris. Organ weights expressed as a percentage of body weight of bhGH and rec-IGF-I treated dwarfs were similar except for the relative weight of the heart of the bhGH group, which was significantly increased compared to the controls and the rec-IGF-I group. These data resolve the issue as to whether or not pure SM-C/IGF-I will induce growth in length and demonstrate the usefulness of recombinant IGF-I in the studies of growth regulation.