CONSUMPTION OF AMINO-ACIDS BY BOVINE PREIMPLANTATION EMBRYOS

Bovine embryos produced in vitro from the putative zygote stage to the blastocyst stage, and blastocysts freshly flushed from the uterus, we re cultured in a physiological mixture of amino acids. Depletion of am ino acids from the medium and, in a few cases, their appearance, was m easured by high performance liquid chromatography. Amino acids were de pleted at widely differing rates. The depletion of amino acids was hig her when embryos at later developmental stages were cultured, implying an increase in amino acid requirement with development. Threonine was the only amino acid to be depleted at all stages of development; depl etion increased from 0.18 +/- 0.07 pmol embryo(-1) h(-1) at the putati ve zygote stage to 1.96 +/- 0.49 pmol embryo(-1) h(-1) at the blastocy st, stage. Glutamine was depleted at the putative zygote stage and the 4-cell stage (0.76 +/- 0.05 and 0.94 +/- 0.10 pmol embryo(-1) h(-1) r espectively), but was not significantly depleted at the later stages. Alanine was the only amino acid that appeared consistently in the medi um and its production increased progressively throughout development. Aspartate, glutamate, threonine and lysine were depleted significantly by blastocysts derived both in vitro and in vivo; the embryos in vivo also depleted arginine, phenylalanine, isoleucine and tyrosine. These results indicate that individual amino acids are depleted at differen t rates by bovine preimplantation embryos and suggest that amino acid requirements change during development.