Amino acids and ammonium

Abstract

Introduction The introduction of amino acids to the culture media for the mammalian oocyte and embryo is arguably the most important advance made in regards to the successful culture of viable embryos. Currently all media for the culture of human embryos contain amino acids as a core component of their formulation. Amino acids are molecules containing an amine group (NH2) as well as a carboxylic acid group (COOH) and a variable side chain. In mammals there are 20 proteinogenic amino acids that are naturally incorporated into polypeptides within the body, while some other organisms have 22 (Table 8.1). Traditionally amino acids have been shown to be important in cellular metabolism and in many organisms as energy substrates and osmolytes. However, there is growing evidence in other tissues that amino acids are able to control many cellular functions including regulation of cell signaling and gene expression. Interestingly, although it is clear that their addition to a culture medium formulation improves embryo development and viability, the cellular function of amino acids in regulating embryo development is largely unknown. This chapter will review the current knowledge and history of the use of amino acids in culture media for the mammalian embryo as well as the in vitro artifact of by-product accumulation of ammonium in the medium.