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Variability of glutathione S-transferase alpha in human liver and plasma
T P Mulder1, D A Court, W H Peters
1Department of Gastroenterology, University Hospital St. Radboud, 6500 HB Nijmegen, The Netherlands.
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 variability of class alpha glutathione S-transferases in human liver, where they are highly expressed, or in serum.
Methods:
Both total class alpha glutathione S-transferase (GST-alpha, composed of GSTA1-1, GSTA1-2, and GSTA2-2) as well as GSTA1-1 concentrations were measured 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-alpha and GSTA1-1 in liver cytosols were 25.1 +/- 9.4 and 10.7 +/- 5.3 microg/mg protein, respectively, and did not correlate with activities of aspartate aminotransferase or alanine aminotransferase. The mean total GST-alpha in liver was significantly higher in females compared with males (28.8 +/- 10.0 vs 22.0 +/- 7.8 microg/mg protein; P <0.05). In contrast, the median total GST-alpha in plasma was lower in females compared with males (2.0 and 2.8 microg/L, respectively; P <0.0001). The median ratios for GSTA1-1/total GST-alpha in liver and plasma were 0.42 and 0.58, respectively.
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 values in males.