Abstract:
The role of exogenous protein during bovine pre-implantation embryodevelopment in two in vitro production systems wasinvestigated. Morphological development, survival after vitrification andmetabolic activity before and after vitrification were recorded in blastocystsgenerated in vitro in synthetic oviduct fluid (SOF)medium in the presence of either bovine serum albumin (BSA) orpolyvinyl-alcohol (PVA). Metabolic activity was determined by measuring oxygenconsumption, glucose and pyruvate uptake as well as lactate production.Development to blastocysts and survival after vitrification were reducedsignificantly in medium lacking protein. Of the metabolic parameters measured,only pyruvate uptake was increased significantly in embryos cultured in mediumsupplemented with PVA. Whereas in BSA-supplemented medium pyruvate uptake wascorrelated with lactate production, in PVA-supplemented medium glucose uptakewas correlated with lactate production. Lactate production increasedsignificantly after vitrification as compared with fresh embryos. Thus,exogenously added protein significantly alters oxidative metabolism. In mediumlacking protein, the additional pyruvate may be used for the maintenance ofintracellular amino acid pools. Vitrification appears to alter glycolyticmetabolic profiles indicating a stress-response. In conclusion, the perturbedmetabolism corresponding to reduced developmental capacity of embryos producedunder protein-free conditions emphasizes the ambiguity between maximumdevelop-ment, technical and hygienic requirements and physiological demands ofthe early bovine embryo in vitro. The use ofwell-defined recombinant proteins might assist in closing this gap.