[25] Purification of rat insulin-like growth factor II

Dulak and Temin first described the purification of multiplication-stimulating activity (MSA) or rat IGF-II (rIGF-II) from serum-free medium conditioned by the BRL-3A rat liver cell line. Results of biosynthetic labeling experiments suggest that the various size rIGF-II species are derived from a common pro-rIGF-II (∼20 kDa). The smallest rIGF-II species (MSA-III-2) has the highest specific activity in radioreceptor assays and bioassays, and it is most easily purified to homogeneity. However, greater quantities of the 8700-Da species (MSA-II) are produced by the BRL-3A cells, and a mixture of MSA-II species can be obtained by following a two-step purification procedure. This chapter discusses the culture of the BRL-3A rat liver cell line and the measurement of rIGF-II during purification. The chapter also discusses rat IGF-II purification and evaluates rIGF-II preparations.