SUMMARY of this research was to localize steroid homone synthesis The aim (progesterone and estrogen) in the bovine placenta at different stages of pregnancy, using immunohistocchemical technique (peroxidase anti peroxidase). Twenty-one gravid bovine uteri at various stages of pregnancy were investigated. Placenta tissues (fetal and maternal) were fixed in paraformaldehyde and glutaraldehyde or snapfrozen without any fixation. The immunohistochemical staining of placenta tissues was
positive with antibody to progesterone for all stages of pregnancy investigated. Whereas no immunoreactive production for estrogen was observed before parturition, it appears clearly on the sample collected during parturition (Cesarean Section) and was localized solely in binucleate giant cells.