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.

Increased level of organochlorine pesticides in chronic kidney disease patients of unknown etiology: role of GSTM1/GSTT1 polymorphism

Chronic kidney disease (CKD) of unknown etiology represents about 16% of CKD patients in Indian subcontinents and 10% worldwide. The aetiology of CKD of unknown etiology remains unclear though epidemiological studies indicate the involvement of the environmental toxins. Organochlorine pesticides (OCPs) have been detected in general population in India. It is possible that polymorphism of xenobiotic metabolizing enzymes (XMEs) may play an important role in this process. In this we intend to find out blood levels of OCPs in CKD patients of unknown etiology and to evaluate the consequence of glutathione S-transferase (GST) gene polymorphism on the same. We have assessed 270 CKD patients and 270 age-sex-matched healthy controls for this study. The blood OCP levels were analyzed by gas chromatograph. GSTM1, GSTT1 genotyping were carried out by multiplex PCR. Blood levels of HCH, endosulfan and total pesticides were significantly higher in CKD patients and negatively correlated with eGFR. The combined frequency of GSTM1(-)/GSTT1(-) genotype increased the risk of CKD by 1.8-fold as compared to healthy controls. To find out the dependence of blood OCPs level on genotype, we carried out logistic regression analysis and results revealed that GSTM1(-)/GSTT1(-) genotype associated significantly with a number of OCPs namely γ-HCH, p,p'-DDT and total pesticides. Polymorphism of XMEs not only increased accumulation of pesticides but also aggravates kidney dysfunction as evident from significant decrease in eGFR.