Adipogenic activities in commercial preparations of fetuin.

Fetuin is frequently in use as a serum substitute especially during the culture of differentiating preadipocyte cell lines. We show here, that the commercially available crude Pedersen fetuin contains a factor permissive for adipose conversion. It can be separated from fetuin by dialysis at acid pH. When 3T3-L1 cells are cultured in the presence of purified Pedersen fetuin, they fail to undergo adipose conversion unless this permissive adipogenic factor is added to the culture medium. Insulin-like growth factor I (IGF-I) and growth hormone (GH) are not able to replace the factor.