NMR and pattern recognition studies on liver extracts and intact livers from rats treated with α-naphthylisothiocyanate

Abstract

The metabolite profiles from livers of toxin-treated rats were investigated using high resolution 1 H NMR spectroscopy of aqueous (acetonitrile/water), lipidic (chloroform/methanol) extracts and magic angle spinning (MAS)-NMR spectroscopy of intact tissue. Rats were treated with the model cholestatic hepatotoxin, α-naphthylisothiocyanate (ANIT, 150 mg/kg) and NMR spectra of liver were analysed using principal components analysis (PCA) to extract novel toxicity biomarker information. 1 H NMR spectra of control aqueous extracts showed signals from a range of organic acids and bases, amino acids, sugars, and glycogen. Chloroform/methanol extracts showed signals from a range of saturated and unsaturated triglycerides, phospholipids and cholesterol. The MAS 1 H NMR spectra of livers showed a composite of signals found in both aqueous and lipophilic extracts. Following ANIT treatment, 1 H NMR-PCA of aqueous extracts indicated a progressive reduction in glucose and glycogen, together with increases in bile acid, choline, and phosphocholine signals. 1 H NMR-PCA of chloroform/methanol extracts showed elevated triglyceride levels. The 1 H MAS-NMR-PCA analysis allowed direct detection of all of the ANIT-induced tissue perturbations revealed by 1 H NMR of extracts, enabling metabolic characterisation of the lesion, which included steatosis, bile duct obstruction and altered glucose/glycogen metabolism. MAS-NMR spectroscopy requires minimal sample preparation and, unlike 1 H NMR spectroscopy of tissue extracts, does not discriminate metabolites based on their solubility in a particular solvent and so this is a particularly useful exploratory tool in biochemical toxicology.