The body is composed of 2 major compartments, fat and fat-free mass.  Fat-free mass consists of water, inorganic matter (e.g. minerals) and organic matter (e.g. protein, DNA). One can determine total body water via the initial dilution of ²H-labeled water.  Fat mass can be calculated assuming a constant relationship between water and inorganic and organic matter in fat-free mass.

This test requires a single injection of ²H-labeled water and the collection of 1 blood sample 2.5 hours post-injection.

Note: This test does not require catheterized mice, nor does it require that mice be shipped to the MMPC.  The isotopes are non-radioactive and no special safety precautions are required, the tracers will be shipped from the MMPC to the investigator.  Investigators will be instructed on how to administer the isotopes, collect samples and then ship them back to the MMPC.