Binding of I-125-insulin-like growth factor-II to cells cultured in fetal bovine serum: a complication

Insulin-like growth factor II is an important fetal mitogen in mice and hum ans and its biological activity is regulated in a complex manner. The pepti de interacts with three membrane-bound receptors, with a superfamily of ins ulin-like growth factor binding proteins and with the proteoglycan, glypica n-3, Recently, the blood protein, vitronectin, has been identified as a nov el insulin- like growth factor II-binding protein. Many studies have used c ell lines maintained in fetal bovine serum to identify cell surface insulin -like growth factor II binding sites. We now describe a complication associ ated with the interpretation of such in vitro studies. Fetal bovine serum-d erived vitronectin adheres very tightly to tissue culture dishes. When cell s that have been maintained in fetal bovine serum are incubated with I-125- insulin-like growth factor II, a substantial fraction of the I-125-insulin- like growth factor II apparently associated with the cell surfaces may repr esent radioliogand bound by the fetal bovine serum-derived vitronectin. Thi s may result in over-estimation of cell surface insulin-like growth factor II binding sites. (C) 2000 Elsevier Science Ltd. All rights reserved.