Fluorodeoxyuridine affects the identification of metabolic responses to daf-2 status in Caenorhabditis elegans

Fluorodeoxyuridine (FUdR) is often used to help maintain synchronous populations of Caenorhabditis elegans adults, for instance as would typically be the case in studying age-related effects. However, given that FUdR inhibits DNA synthesis and therefore reproduction, it will clearly have significant wide-ranging biological effects. It is often assumed that these can be compensated for using appropriate controls. We show here that this is not the case for a metabolomic analysis of a long-lived daf-2 mutant strain: not only were the effects of FUdR much greater than the effects of the mutation, there were clear interactions between FUdR and genotype, such that identification of daf-2-dependent metabolites would have been compromised on FUdR plates. This indicates that FUdR should only be used with caution for C. elegans ageing experiments, and should not be assumed to be independent of other factors being studied.