Effects of Hormone Replacement Therapy on Plasma Glutathione S-Transferase A1-1 Concentrations in Healthy Postmenopausal Women

Abstract

Glutathione S -transferases (GST, EC 2.5.1.18) are detoxification enzymes that catalyze the addition of glutathione to a wide variety of xenobiotics. Cytosolic GSTs are dimeric proteins and are divided into four classes: alpha, mu, pi, and theta (1). More than 2% of the soluble protein in the liver consists of class alpha GST. These enzymes are released in considerable quantity into the bloodstream during hepatocellular damage. Because class alpha GSTs have a short plasma half-life (±1 h), its concentration will follow changes in acute hepatocellular damage more accurately than will concentrations of the aminotransferases (2). Two class alpha subunits have been identified, and both homodimers (GSTA1-1 and GSTA2-2) and the heterodimer (GSTA1-2) have been purified from human liver (2). Tiainen and Karhi (3) were the first to report that men had significantly ( P <0.02) higher plasma GST-alpha concentrations than women, which was confirmed recently by our group in a much larger study population (median plasma GSTA1-1 concentration in 175 men, 1.92 μg/L, and in 175 women, 1.28 μg/L (4)). However, in women but not in men, a significant increase with age was noted: The median plasma GSTA1-1 concentration in 83 women at ages 20–40 years was 1.08 …