TOPOGRAPHY OF GROWTH-HORMONE RECEPTOR EXPRESSION IN THE BOVINE EMBRYO

Using in situ hybridization, mRNA encoding the growth hormone receptor (GHR) was localized in preimplantation embryos produced by in vitro f ertilization (IVF) as well as in 30- to 70-day-old bovine embryos. In IVF embryos the transcript of GHR was demonstrated in the inner cell m ass of 8-day-old blastocysts. In 30-day-old embryos, the mesonephros w as the first organ to express the mRNA of GHR. In 40-day-old embryos, the transcript was found in the neurones of the spinal ganglions, the splanchnic nerves and the motoneurones of the spinal cord, in the vasc ular endothelium, and in the developing striated muscle tissue. Coloca lization of the protein by immunohistochemistry showed an identical di stribution pattern of GHR in 30- to 70-day-old embryos.