Abstract
FOLSTAD et al.13) were the first who succeeded in cultivating rat embryo from eight-cell stage to blastocyst. The present investigation was undertaken to determine what amino acids are necessary during such development. The eight-cell embryos were obtained from Wistar rat on the day-4 of pregnancy (the day when spermatozoa were found in the smear was counted as day-1), and embryos were cultured by the method of BRINSTER10). The basal medium used in all experiments was BMOC214). The eight-cell embryos could develop to blastocysts in a medium either containing carbohydrate as energy source or a nitrogen source alone (Table 1). Out of 165 eight-cell embryos incubated, 99 developed to morulae or blastocysts when sodium pyruvate, sodium lactate and 1% BSA were added to the medium (Table 2).Glycine, glutamic acid, glutamine, alanine, arginine, serine, valine, aspartic acid and threonine seemed beneficial for the development beyond eight-cell stage, but isoleucine, phenylalanine, tryptophan and tyrosine were without effect (Table 3). Of 97 embryos, 66 developed to morulae or blastocysts when sodium pyruvate, lactate and five amino acids, i.e., alanine, glycine, glutamic acid, threonine, and serine were present in the medium (Table 4). In a medium containing sodium pyruvate, sodium lactate and amino acids as in the uterine fluid on the 5th day of pseudopregnancy, 161 of 192 embryos incubated developed to morulae or blastocysts (Table 5), suggesting that the utilization of amino acids by the embryo might be closely correlated with the content of the free amino acids in the corresponding uterine fluid.
