INDUCTION OF EARLY-PREGNANCY FACTOR ACTIVITY IN-VITRO BY PLATELET-ACTIVATING-FACTOR IN MICE

The rosette inhibition test was used to determine early pregnancy fact or activity in culture media from oestrous mouse ovaries and oviducts stimulated in vitro for early pregnancy factor production under differ ent experimental conditions. Embryo conditioned media, platelet-activa ting factor and cortical granule release media could all stimulate the production of early pregnancy factor by oestrous mouse ovaries and ov iducts, This stimulation was completely blocked by the presence of BN 52021, a platelet-activating factor receptor antagonist. This study in dicates that platelet-activating factor is the 'ovum factor' released by the zygote on fertilization to initiate the synthesis of early preg nancy factor.