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 regulator of fe tal growth and differentiation. IGF bioavailability is modulated by IGF bin ding proteins (IGFBPs). me 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 a ssay, Western blotting, and by immunohistochemistry on sections of mouse em bryos of 13.5 days post coitum. Specificity for the IGFBP-2 through -6 anti sera also was confirmed immunohistochemically in liver and lung of correspo nding gene deletion (knock-out) mutant mice and wild-type litter mates. Immunohistochemistry and messenger RNA (mRNA) in situ hybridization on sect ions of mouse embryos of 13.5 days post coitum revealed tissue-specific exp ression patterns for the six IGFBPs. The only site of IGFBP-1 protein and m RNA production was the Liver. IGFBP-2, -4, and -5 protein and mRNA were det ected in various organs and tissues. IGFBP-3 and -6 protein and mRNA levels mere low. In several tissues, such as lung, liver, kidney, and tongue, mor e than one IGFBP (protein and mRNA) could be detected. Differences between mRNA and protein localization were extensive for IGFBP-3, -5, and -6, sugge sting that these IGFBPs are secreted and transported. These results confirm the different spatial localization of the IGFBPs, on the mRNA and protein level. The overlapping mRNA and protein localization f or IGFBP-2 and -4, on the other hand, may indicate that these IGFBPs also f unction in an auto- or paracrine manner.