Variability of glutathione S-transferase alpha in human liver and plasma

Background: Glutathione S-transferases are a family of enzymes involved in the binding, transport, and detoxification of a wide variety of endogenous and exogenous compounds. Little information is available about the variabil ity of class cw glutathione S-transferases in human liver, where they are h ighly expressed, or in serum. Methods: Both total class a glutathione S-transferase (GST-alpha, composed of GSTA1-1, GSTA1-2, and GSTA2-2) as well as GSTA1-1 concentrations were me asured by specific and sensitive ELISA in liver cytosols of 35 organ donors and in plasma samples of 350 healthy controls. Results: The mean total GST-a and GSTA1-1 in liver cytosols were 25.1 +/- 9 .4 and 10.7 +/- 5.3 mu g/mg protein, respectively, and did not correlate wi th activities of aspartate aminotransferase or alanine aminotransferase. Th e mean total GST-alpha in liver was significantly higher in females compare d with males (28.8 +/- 10.0 vs 22.0 +/- 7.8 mu g/mg protein; P < 0.05). In contrast, the median total GST-a in plasma was lower in females compared wi th males (2.0 and 2.8 mu g/L, respectively; P < 0.0001). The median ratios for GSTA1-1/total GST-alpha in liver and plasma were 0.42 and 0.58, respect ively. Conclusions: GSTA1-1 constitutes approximately one-half of the total amount of alpha class GSTs in human plasma and liver. Total GST-alpha values are higher in female liver but lower in plasma compared with the respective val ues in males. (C) 1999 American Association for Clinical Chemistry.