Real-time monitoring of the metabolic capacity of ex vivo rat olfactory mucosa by proton transfer reaction mass spectrometry (PTR-MS)

Olfactory mucosa (OM) can metabolise odorant volatile organic compounds through various enzymatic mechanisms to produce odorous or non-odorous metabolites. Preliminary ex vivo studies using headspace-gas chromatography (HS-GC) revealed the formation of metabolites when odorant molecules were injected in the headspace above a fresh explant of rat olfactory mucosa. However, this method did not allow accessing the data during the first 5 min of contact between the odorant and the mucosa; thus limiting the olfactory biological significance. Using a direct-injection mass spectrometry technique with a proton transfer reaction instrument (PTR-MS), we have been able, for the first time, to investigate the first moments of the enzymatic process of the metabolic capacity of ex vivo rat olfactory mucosa in real time. Using ethyl acetate as a model volatile odorous substrate, we demonstrated here for the first time that this odorant could be metabolised by an ex vivo olfactory mucosa within seconds, producing ethanol as metabolite.