Analysis of stimulatory and inhibitory amino acids for development of hamster one-cell embryos in vitro

Hamster embryo development to the blastocyst stage in vitro can be modulated by amino acids. This series of experiments employed both empirically and statistically designed approaches to elucidate which of 20 amino acids inhibit or stimulate development and to devise a complement of amino acids that best supports in vitro development of hamster 1-cell embryos. Development and/or mean cell number were significantly inhibited by the presence of leucine, tyrosine, valine, isoleucine, phenylalanine, arginine, methionine, or cysteine (at 0.5 mM) and isoleucine, phenylalanine, or tryptophan (at 0.05 mM). Three amino acids--glutamine, taurine, and glycine--were stimulatory and in combination improved development; the culture medium containing these amino acids was designated Hamster Embryo Culture Medium-5. Moreover, addition of another eight amino acids--asparagine, aspartic acid, serine, glutamic acid, histidine, lysine, proline and cysteine (medium designated HECM-6)--had a significant stimulatory effect on development over previously formulated culture media for hamster embryos. These results demonstrated that amino acids, alone and in combination, can markedly stimulate or inhibit hamster embryo development in vitro up to the blastocyst stage. Embryo transfer experiments showed that HECM-5 and -6 (chemically defined, protein-free culture media) supported normal preimplantation embryo development in vitro. This study also indicates that empirically designed embryo culture media formulations can be as effective as those obtained by application of statistical methodologies.