Platelet aggregating activity in human embryo culture media free of PAF-acether

A factor activating human platelets and liberated by the embryo was sought in the culture media of human embryos using two bioassays. The first bioassay demonstrated the existence of a thrombocytopaenic factor after the i.p. injection of culture media into splenectomized mice. This factor was found more frequently in media which contained an embryo compared to those which contained a non-fertilized oocyte. PAF-acether (1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine) was searched for with a specific bioassay, using washed rabbit platelets. This remained negative for all the media studied, including those which had contained an embryo giving rise to a pregnancy. In these experiments it was not possible to relate embryo-derived platelet activating factor (EDPAF) to PAF-acether. Neither were we able to use the detection of EDPAF to test embryonic viability, or attempt to identify those embryos which were susceptible to lead to a pregnancy after intrauterine transfer from among all the embryos transferred.