The process begins with the introduction of a stable isotope-labeled compound into a biological system, such as a cell culture or an animal model. As the labeled compound is metabolized, the isotopic label is incorporated into intermediate and end products of metabolic pathways. By using techniques such as mass spectrometry or nuclear magnetic resonance (NMR) spectroscopy, researchers can detect and quantify the labeled metabolites, allowing them to map out metabolic pathways and measure fluxes.
