EFFECT OF HIGH-MOLECULAR-WEIGHT FACTORS PRESENT IN BOVINE OVIDUCT-CONDITIONED MEDIUM ON IN-VITRO BOVINE EMBRYO DEVELOPMENT

To investigate the presence of embryotrophic factors in bovine oviduct -conditioned medium (BOCM), the high molecular weight fraction (>10 KD a) from BOCM was added to 3 chemically defined embryo culture media (T CM199, DMEM/F12 and modified synthetic oviduct fluid [mSOF]). Zygotes were obtained by in vitro maturation and fertilization of oocytes. Con ditioning of TCM 199 with oviduct cells increased both cleavage to the 5- to 8-cell stage (59 vs 37%) and further development to the blastoc yst stage (19 vs 1%). The low molecular weight fraction (<10 KDa) of B OCM maintained development to the 5- to 8-cell stage but did not allow development to the blastocyst stage. Adding the high molecular weight fraction to the inactive low molecular weight fraction restored bovin e embryo development up to the blastocyst stage. This embryotrophic ef fect of the high molecular weight fraction was not observed when this fraction was added to TCM199 or DMEM/F12 medium. Whereas adding this f raction to mSOF medium significantly (P<0.05) increased embryo develop ment up to the blastocyst stage (36%) in comparison with that of mSOF (15%) or BOCM (14%). These results show that BOCM contains high molecu lar weight factors promoting embryo development up to the blastocyst s tage. Some chemically defined media mask the effect of these embryotro phic factors.