Identification of a potent neurotrophic substance for ciliary ganglionic neurons in fetal calf serum as insulin-like growth factor II

When fetal calf serum (FCS) alone is used as a trophic support for cultured chicken parasympathetic ciliary ganglionic (cCG) neurons, it does not show any survival-promoting effects on these neurons, When FCS is applied to he parin-affinity chromatography, however, potent survival-promoting activity is obtained in the fraction eluted,vith 0.5 M NaCl, Using cCG neurons as a bioassay system, this neurotrophic activity was purified by a combination o f heparin-affinity chromatography, gel filtration chromatography, and Sep-P ak C18 cartridge. The 40-50-kDa fractions from the gel filtration column,vi th strong survival-promoting activity were shown to contain insulin-like gr owth factor II (IGF-II) by immunoblot analysis. By acidification, the survi val-promoting activity and IGF-II were translocated together from the 40-50 -kDa to the 7-10-kDa fractions, and the survival-promoting activity in the 7-10-kDa fractions was blocked by an anti-IGF-II neutralizing monoclonal an tibody. These results indicate that the neurotrophic substance in 0.5 M NaC l-eluate from heparin-affinity chromatography is IGF-II and that mechanisms may exist in vivo for the activation of latent IGF-II, whose biological ef fects may be blocked by its specific binding proteins. J, Neurosci, Res. 56 :386-396, 1999, (C) 1999 Wiley-Liss, Inc.