Combinatorial approach of LC-MS/MS and LC-TOF-MS for uncovering in vivo kinetics and biotransformation of ochratoxin A in rat

A combinatorial platform of liquid chromatography-tandem mass spectrometry (LC-MS/MS) and liquid chromatography coupled with time of flight mass spectrometry (LC-TOF-MS) has been developed to investigate the in vivo kinetics and biotransformation of ochratoxin A (OTA) in rats. The stable isotope dilution LC-MS/MS method was first validated by determining the linearity (R-2 >= 0.9990), sensitivity (lower limit of quantitation of 0.05 ng mL(-1)), accuracy (83.3-108.3), precision (RSD <= 15.6%) and stability (>= 75.0%), and was approved for the determination OTA in plasma, heart, liver, spleen, lung, kidney and brain with a run time of 7.0 min. Simultaneously, an LC-TOF-MS method could unambiguously identify the metabolites of OTA in a total run time of 14 min. The subsequent studies on kinetics and distribution after oral administration of 0.2 mg/kg b.w. OTA in rat indicated that OTA could reach a maximum value of 1932.4 +/- 124.9 ng mL(-1) within 5 h due to its fast absorption, and then was slowly eliminated in plasma with a half-life time (t(1/2)) of 75.6 +/- 29.0 h. Results of tissue accumulation after a daily oral administration of 0.1 mg/kg b.w. OTA during 20 days showed that the highest concentration of OTA was observed in lung (95.9 +/- 13.7 ng g(-1)), followed by liver (76.0 +/- 9.7 ng g(-1)), heart (62.0 +/- 4.2 ng g(-1)) and kidney (55.7 +/- 4.7 ng g(-1)). Furthermore, three less toxic metabolites of OTA were clearly identified: Ochratoxin beta (OT beta) and ochratoxin B (OTB) methyl ester were found in kidney and spleen, respectively, while phenylalanine was detected in heart and kidney. Thus, a possible metabolic pathway of OTA was proposed. The above achieved results justified that the application of combinatorial LC-MS/MS and LC-TOF-MS methods are valuable tools to uncover the kinetics and metabolism of OTA for the interpretation of toxicological findings in animals and extrapolation of the resulting data as reference to humans. (C) 2013 Elsevier B.V. All rights reserved.