The insulin-like growth factor autocrine/paracrine system consists of the insulin-like growth factors (IGF-I and IGF-II), Type I and Type II IGF receptors, and proteins that modulate the availability of the IGFs to their target cells, called IGF binding proteins (IGFBPs). The IGFs are low molecular weight peptides with mitogenic activity in a variety of tissues, and with regard to the female reproductive tract, the IGF system is present in ovary and uterus. In ovarian folliculogenesis, IGF-I peptide is estradiol- and gonadotropin-dependent, and the Type I IGF receptor is also gonadotropin-dependent. In uterine myometrium, the IGF system is a mediator of estradiol action, and in uterine endometrium, the IGFs appear to be mediators of estradiol and perhaps progesterone action. The role of the IGF autocrine/paracrine system in the oviduct (fallopian tube) is an unexplored area of research. and is the focus of this proposal. The oviduct is a cyclically changing structure in which gamete maturation and transport, fertilization, and early embryo development and transport occur. It is a steroid-responsive tissue whose epithelium undergoes characteristic changes throughout the menstrual cycle, under the influence of steroid hormones. The specific goals of this project are to determine in human oviduct the ontogeny of the IGFs, their receptors, and their binding proteins, in the changing hormonal milieu of the menstrual cycle. Human fallopian tubes from hysterectomy specimens will be used as a source of RNA as well as of epithelial cells for culture. Three sections of the oviduct will be examined (fimbria, ampulla, and isthmus). Tissues from different cycle stages have been exposed to a changing hormonal environment in vivo, and effects on cellular gene expression will then be examined. For oviductal tissue, expression and regulation of IGFBP mRNAs will be studied by Northern analysis, and expression and regulation of IGF peptide and receptor mRNAs will be examined by a ribonuclease protection assay. Oviductal epithelial cells will be cultured in the absence and presence of estradiol and the conditioned medium examined for the synthesis of IGFBPs by Western ligand blot analysis. Identification of the IGFBPs will be performed by immunoprecipitations, using antibodies specific for the IGFBPs. IGFI and IGF-II in conditioned media will be assayed by a sensitive radioimmunoassay. IGF receptors in cultured oviductal epithelial cells will be examined by cross-linking studies and Scatchard analysis. In situ hybridization and immunohistochemical studies in whole tissue will confirm mRNA expression and protein synthesis, respectively, of the IGFs, their binding proteins and receptors, as well as define their cells of origin.
| Giudice, L C; Dsupin, B A; Irwin, J C et al. (1992) Identification of insulin-like growth factor binding proteins in human oviduct. Fertil Steril 57:294-301 |
