Differences in Amino Acid Content of Preimplantation Mouse Embryos that Develop in Vitro Versus in Vivo: In Vitro Effects of Five Amino Acids that are Abundant in Oviductal Secretions1

Abstract

Although it is now well established that amino acids can improve preimplantation development of mouse embryos in vitro, the mechanisms by which they influence development have not been determined. To investigate these mechanisms, we compared the contents of seven abundant amino acids (alanine, aspartate, glutamate, glycine, serine, and taurine) in 4-8-cell embryos and blastocysts developing in vivo with the contents in those developing from the 2-cell stage in vitro. We also studied the effects of five amino acids (alanine, glutamate, glutamine, glycine, and taurine) that are abundant in the oviductal lumen on the amino acid content of embryos developing in vitro. Blastocysts that developed in vitro contained about six times more alanine and about one-sixth as much taurine as blastocysts that developed in vivo, but the same amounts of glycine and serine. In the presence of glycine and four other abundant amino acids in oviductal secretions, however, blastocysts that developed in vitro had higher levels of both glycine and serine than those that developed in vivo. In contrast, glycine either alone or in combination with the other amino acids reduced the alanine content of blastocysts developed in vitro to nearer that of blastocysts developing in vivo. Similarly, taurine in the medium allowed blastocysts developed in vitro to increase their content of this amino acid to normal levels. The levels of taurine and, somewhat surprisingly, glutamine and glycine became abnormally low in embryos within 24 h of the onset of in vitro culture in medium that did not contain the amino acid.(ABSTRACT TRUNCATED AT 250 WORDS)