ABSTRACT
Recently a platelet activating factor (PAF)-like activity has been found in embryo conditioned media (ECM) and consequentially been termed embryo-derived PAF (EPAF). Yet it remains unclear whether the embryo-released molecule is in fact PAF or a PAF precursor or inductor in vivo. In this study we shall show that ECM did not induce platelet aggregation in vitro; however, it was possible to detect PAF-activity using the sensitive splenectomized mouse bioassay (SMB). Following lipid extraction, PAF activity was diminished, and after additional HPLC separation completely lost. We propose that the active fraction of ECM is lipid in nature but that this molecule is not PAF. We would rather suggest that this molecule induces the production of PAF by other cell types in vivo.
