Some of the IGFBPs have been proposed to potentiate IGF actions by forming extracellular matrix associations, facilitating transport to cell-surface receptors, and protecting IGFs from degradation. Other IGFBPs have been shown to inhibit the action of the IGFs by forming an inactive complex (see for review).
One such binding protein, IGFBP-4, was shown to be expressed in the mouse uterus in a temporal pattern that correlated with the time of implantation. Ligand blot analysis of mouse uterine tissue extracts using [125I]IGF-I showed that, in contrast to the other IGFBPs, the ligand binding activity of IGFBP-4 significantly increased at the time of embryo implantation. In situ hybridization studies on periimplantation mouse uteri revealed that IGFBP-4 mRNA localizes to the implantation site and increases dramatically during this period. buy antibiotics online
The specific anatomical and temporal nature of uterine IGFBP-4 mRNA expression during the periimplantation period suggests a physiologic role for this binding protein in the implantation process. However, few studies have been done to determine the factors necessary for expression of IGFBP-4 and IGF-I mRNAs in the mouse uterus during the periimplantation period. To address this issue, we conducted in situ hybridization analysis on pregnant mouse uteri and deciduomata-induced mouse uteri to determine whether the presence of an embryo is a requirement for uterine IGF-I and IGFBP-4 mRNA expression.