The Use of Different MS Techniques to Determine Glutathione Levels in Marine Tissues

Abstract

Several techniques were used, mainly mass spectrometry connected with gas chromatography, matrix-assisted laser desorption with ionization time-of-flight and mass spectrometry connected with liquid chromatography. A major problem was encountered in determining glutathione, which can be conditioned by the pH and selected reducing agents. The GSH form can be oxidized through derivatization, and a small glutathione amount in the biological samples may hinder the determination process. Another problem is the existence of a metal ion in the tested organism; therefore, often a reagent with a chelating function is added to the sample and the mobile phase in liquid chromatography is applied with appropriate polarity for GSH and GSSG. We determined the concentrations of total, reduced, and oxidized glutathione in the liver, hepatopancreas, muscle, and gonad tissues of brown shrimp (Crangon crangon) and fish (Psetta maxima and Clupea harengus membras). The highest concentrations of tGSH were recorded in the shrimp hepatopancreas (7.21 ± 0.011 μmol g−1 wet weight), in herring liver (2.85 ± 0.025 μmol g−1), and in turbot liver (1.86 ± 0.063 μmol g−1). In turn, the highest concentrations were reported for GSSG in the muscle of shrimp (0.140 ± 0.000204 μmol g−1), and in the testis of turbot (0.063 ± 0.000170 μmol g−1) and herring (0.009 ± 0.000015 μmol g−1). We also investigated seasonal changes in the concentrations of glutathione in the muscle of C. crangon shrimp in the annual cycle. The lowest values of total glutathione were recorded during spring and autumn, which could be correlated with the increase in lipid peroxidation and oxidative stress.