EMBRYO METABOLISM

If is very difficult to have a clear and homogenous idea of the embryo metabolism. In fact it may vary from one specy to an other and also a ccording to the embryonic stage : i.e. before and after genomic activa tion. Basic compounds such as glucose may be toxic, but obviously, it is more the probleme of the quantity introduced in the culture media a nd an insuitable balance between the metabolites which may impair the embryonic development At low concentration glucose is actively metabol ised by embryos. High levels of amino acids are deleterious (due to re lease of ammonia), but they are necessary at low concentrations. Addit ion of serum or other biological fluids is generally useless. Further knowledge on embryo metabolism is necessary to avoid culture medium re lated delay or developmental blocks. Sequential media are at least par tly the answer.