• As a polypeptide hormone, insulin has multiple metabolic (catabolic) effects on mammalian cells, promoting glucose and amino acid uptake, fat production, monovalent cation and phosphate transport, and protein and nucleic acid synthesis.
• As a carrier of iron, transferrin can also help reduce the toxic levels of oxygen free radicals and hydrogen peroxide.
• Selenite is a cofactor of glutathione peroxidase and other proteins and is used as an antioxidant in culture media.
• Ethanolamine plays an important role in the proliferation of mammalian cells and it is a precursor of phosphoethanolamine, the head group of a type of phospholipids important for plasma membrane synthesis.

ITS is recommended for the supplementation of RPMI-1640 and Earle's culture media.