ABSTRACT
Two principal classes of insulin-like growth factor (IGF) have been demonstrated by amino acid and DNA sequence analysis: insulin-like growth factor I (IGF-I), or somatomedin C (Sm-C), and insulin-like growth factor II (IGF-II). Currently, the generic terms “insulin-like growth factor” and “somatomedin” are used interchangeably, while the terms “IGF-I” and “IGF-II” are in predominant use for the specific peptides. The effect of IGF-I on the structure of the final proteoglycan product is somewhat controversial. When glycosaminoglycans (GAGs) produced by somatomedin-stimulated and unstimulated control species cartilage were fractionated by Sephadex 200 chromatography, the growth factor was observed to shift the molecular weight distribution of the GAGs to a larger range, suggesting a somatomedin effect on GAG chain length. The role of IGF-I and GH in regulating growth plate cartilage may also involve control of cell differentiation. During the search for improved bioassays for somatomedins, articular chondrocytes were among the cell types chosen for analysis.
