Human cGST enzymes are expressed in the cytosol of all organ tissues examined, although their involvement in xenobiotic metabolism is due principally to enzymes expressed in the liver, intestine, and kidney.127
Tissue-specific ontogenic expression of GST has been demonstrated for hepatic GSTA1 and GSTA2, both of which were detected as early as 10 weeks' gestation age, increasing to adult levels within the first 2 years of life.25 GSTM(1-5) was also detected in fetal liver samples, albeit at lower levels, and increased to adult levels following birth. In contrast, GSTP1 expression has been detected in fetal liver samples (10-22 weeks' gestation age), but declined in the second and third trimester and was virtually undetectable in adult samples. In the fetal lung, GSTP1 is the major GST isozyme, detectable in lung tissue at less than 20 weeks' gestation, and decreased continuously in the developing fetus and infant after birth. In fetal kidney at less than 20 weeks' gestation, both GSTA1 and GSTA2 were detected and increased to adult levels within the first 2 years of life. GSTM levels, however, decreased between the fetal and postnatal samples, while GSTP1 levels remained constant during kidney development.
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