identification of luteinizing hormone releasing hormonelike immunoactivity in ovine cotyledons luteinizing hormone releasing hormone lhrhlike immunoactivity has been identified in cotyledonary extracts prepared from pregnant ewes this activity displayed similar physicochemical properties as synthetic lhrh as determined by reversephase hplc and sizeexclusion hplc under reversephase conditions cotyledonary lhrhlike immunoactivity displayed a retention time 105 01 min which was not significantly different from that of synthetic lhrh when subjected to sizeexclusion hplc cotyledonary lhrhlike immunoactivity eluted in fractions which corresponded to a molecular weight range of 11001200 da which was not significantly different from the elution profile observed for synthetic lhrh the cotyledonary tissue content of lhrhlike immunoactivity averaged 94 24 pgmg n 6 the results of this study demonstrate the presence of lhrhlike immunoactivity in ovine cotyledons although placental synthesis of lhrhlike immunoactive material has been demonstrated in other species it remains to be established whether this activity demonstrated in ovine placenta is the consequence of de novo placental synthesis or represents uptake from the maternal andor fetal circulation