The polymorphic pattern of somatomedins during human development

Human somatomedins (Sm) are heterogeneous on separation by chromatofocussing. Besides the 'classic' insulin-like growth factor I and II (IGF-I/Sm-C and IGF-II), a number of minor peaks emerge which can be classified as IGF-I/Sm-C-like or as IGF-II-like. The aim of the current study was to investigate whether or not polymorphism of somatomedins is present in individuals and whether or not the polymorphic pattern changes during development. Serum extracts from normal healthy children and adults were fractionated by chromatofocussing and the various somatomedin-like peptides were quantitated by specific radioimmunoassays for IGF-I/Sm-C or IGF-II. The results demonstrate 1) that heterogeneity of somatomedins is a common phenomenon existing in all individuals studied, and 2) that the polymorphic patterns of the IGF-I/Sm-C-family and of the IGF-II-family remain rather stable during development, although minor changes are evident.