Media composition: energy sources and metabolism.

The preparation of defined culture media for embryo development has progressed from simple chemically defined media based on Krebs-Ringer bicarbonate, supplemented with glucose, bovine plasma albumin, antibiotics and utilizing a CO(2)-bicarbonate buffering system to more complete systems based around studies on the physiology and metabolism of the mammalian embryo. Although the concentration of substrates used in media can vary, there are many components that are quintessentially important for embryo development such as energy sources, that play a vital role in regulation of metabolism and hence viability. Here we describe the role of energy substrates within culture media and outline assays which can be utilized to measure embryo metabolism as a mechanism for determining embryo physiology and viability.