Mitogenicity of the earthworm's (Eisenia foetida) insulin-like proteins.

1. Biologically active glycolipoprotein complex (G-90), isolated from whole earthworm tissue extract (Eisenia foetida), was separated into seven fractions by gel-filtration. 2. It has been shown by radioimmunoassay that each of the fractions, except the lightest one, is cross-reactive with porcine anti-insulin antibodies. Molecules that possess such activity were detected by immunoblotting. 3. All fractions, except the heaviest and the lightest one, stimulate mammalian normal and transformed cell proliferation in serum-free conditions in vitro. The intensity of stimulation depends on cell type. Stimulation is completely abolished if the medium is supplemented with fetal calf serum.