Insulin-like growth factor binding proteins are transcribed by preimplantation mouse embryos

Preimplantation embryos have been reported to synthesize insulin-like growth factors (IGF) and their receptors, and reproductive tract fluid has been found to contain insulin and IGF I. In this communication, we report that all stages of preimplantation mouse embryos transcribe IGF binding proteins (IGF-BP) 2, 3 and 4, and that blastocysts also transcribe IGF-BP6. IGF-BP5 was not detected at any preimplantation stage. Reproductive tract cells in proximity to preimplantation mouse embryos transcribe all of IGF-BP2 through 6. Thus studies of the mechanisms of IGF action on preimplantation mouse development must consider the IGF-BP.