Generation of Antisera to Mouse Insulin-Like Growth Factor Binding Proteins (IGFBP)-1 to -6: Comparison of IGFBP Protein and Messenger Ribonucleic Acid Localization in the Mouse Embryo

The insulin-like growth factor (IGF) system is an important reg- ulator of fetal growth and differentiation. IGF bioavailability is mod- ulated by IGF binding proteins (IGFBPs). We have generated six different antisera, directed to synthetic peptide fragments of mouse IGFBP-1 through -6. The specificity of the produced antisera was demonstrated by enzyme-linked immunosorbent assay, Western blot- ting, and by immunohistochemistry on sections of mouse embryos of 13.5 days post coitum. Specificity for the IGFBP-2 through -6 antisera also was confirmed immunohistochemically in liver and lung of cor- responding gene deletion (knock-out) mutant mice and wild-type lit- ter mates. Immunohistochemistry and messenger RNA (mRNA) in situ hy- bridization on sections of mouse embryos of 13.5 days post coitum revealed tissue-specific expression patterns for the six IGFBPs. The only site of IGFBP-1 protein and mRNA production was the liver. IGFBP-2, -4, and -5 protein and mRNA were detected in various organs and tissues. IGFBP-3 and -6 protein and mRNA levels were low. In several tissues, such as lung, liver, kidney, and tongue, more than one IGFBP (protein and mRNA) could be detected. Differences between mRNA and protein localization were extensive for IGFBP-3, -5, and -6, suggesting that these IGFBPs are secreted and transported.