Real time monitoring of the metabolic capacity of ex-vivo rat olfactory mucosa by continuous on-line PTR-MS

It has been evidenced that olfactory mucosa (OM) can metabolize inhaled odorous volatile organic compounds (VOCs) through various enzymatic activities. Moreover, it has been hypothesized that the resulting metabolites could be implied in overall aroma sensory perception. The purpose of the present study was to develop a continuous on-line method allowing real time accurate detection of VOCs using the Proton Transfer Reaction Mass-Spectrometry (PTR-MS) technique. A six-way valve was implemented to allow odorant delivery in a two-way circuit whose end was connected to a PTR-MS instrument. A fresh explant of rat OM was placed in the first branch of the circuit, the second one serving as a control. The continuously injection of gaseous ethyl acetate around the ex-vivo rat mucosa resulted in increase of its main metabolite ethanol while a significant depletion of ethyl acetate signal was observed in comparison to the control signal. These results obtained in real-time continuous recording confirmed the previous results obtained using a discontinuous method. The methodology develop here will originally allow to decipher odorant metabolic pathways occurring at the OM level. The PTR-MS technique appears to be a very promising method to investigate odorant metabolism kinetics in real time. Olfaction; PTR-MS; Metabolites, Rat.