Relative abundance and molecular size of immunoreactive insulin-like growth factors I and II in human fetal tissues.
Previous studies which have quantitated tissue mRNA transcripts have suggested that IGF II is expressed in substantially greater amounts than IGF I during human fetal development. However, this has not been tested directly by recovery and quantitation of IGF peptides from fetal tissues. Tissues from human fetuses were extracted in 1 M acetic acid, and insulin-like growth factor (IGF) I and II immunoreactive species separated from the supernatants by acidic gel filtration. When total immunoreactive IGF I or II eluting from Sephadex G50 between approximately 6 and 15 kDa molecular weight was estimated, allowing for likely blood contamination, tissues from five fetuses contained, on average, 230 fM/mg cell DNA IGF I and 690 fM/mg IGF II. The ratio of IGF II: IGF I peptide content varied from 1.6 in muscle to 7.8 in thymus. Separation of tissue supernatants, fetal plasma and fetal fibroblast-conditioned culture medium on Sephadex G75 revealed that immunoreactive IGF II eluted with molecular weights between 8 and 15 kDa, in addition to 7.5 kDa. While fetal tissues contain more IGF II than IGF I immunoreactivity, the likely presence of IGF II peptide does not agree with the great excess of mRNA for IGF II reported previously.
Hill
D J
DJ
Lawson Research Institute, St. Joseph's Health Centre, London, Ontario, Canada.
D004247:DNA / Q000032:analysis; D005333:Fetus / Q000032:analysis*; D005865:Gestational Age; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000032:analysis*; D007335:Insulin-Like Growth Factor II / Q000032:analysis*; D008970:Molecular Weight; D013002:Somatomedins / Q000032:analysis*
D013002:Somatomedins; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II; D004247:DNA