Preimplantation mouse embryos exhibit growth at the blastocyst stage w
hen there is a dramatic increase in protein content between days 4 and
5 after hCG treatment. This increase in protein synthesis requires th
e uptake of amino acids from the surrounding medium, but the consumpti
on of individual amino acids present as a mixture has not been examine
d. We therefore measured the simultaneous depletion of 18 amino acids
by mouse blastocysts in culture on days 4 and 5 after hCG treatment. T
wo culture media were used: one with amino acids present at concentrat
ions largely based on those reported to give optimal rates of embryo d
evelopment (M16/mix AA), and a second with the amino acids each at 0.1
mmol l(-1) (M16/0.1 AA). After derivatization with o-phthaldialdehyde
to yield highly fluorescent products, amino acid concentrations in th
e media were measured by HPLC. On day 4, seven amino acids were deplet
ed from M16/mix AA at rates significantly greater than zero: aspartate
, arginine, glycine, alanine, isoleucine, leucine and lysine; on day 5
, nine amino acids were depleted at significant rates: aspartate, glut
amate, asparagine, tyrosine, methionine, valine, phenylalanine, isoleu
cine and leucine. Average amino acid depletion from M16/mix AA was 32%
greater on day 5 than on day 4. Aspartate, glutamate, arginine, isole
ucine and leucine appeared to be the key amino acids sought by embryos
on both days tested. Embryos grown in amino-acid-containing media app
eared morphologically normal and their volume increased compared with
embryos cultured in the absence of amino acids.