Metabolic labeling is routinely performed with cultured cells (SILAC), ranging from bacteria and yeast to mammalian cells. However, analysis of mammalian tissue allows greater insight into physiology compared to cultured cells. Stable Isotope Labeling of Mammals (SILAM) refers to the in-vivo incorporation of heavy isotopes in living organisms such as rodents. SILAM enables global, relative quantitative analysis of mammalian disease models and provides insights on post-translational modifications (PTMs). In addition, the labeling of an entire proteome generates ideal standards for quantitative proteomics.
In a SILAM experiment, rodents are typically fed with either an isotope-rich or isotope-deficient diet for a certain period before LC-MS analysis of the harvested tissue(s) of interest. Heavy diets can either consist of a mouse feed supplemented with stable isotope labeled amino acids or enriched Arhrospira platensis (Spirulina) used as a source of carbon and nitrogen for the animal.