GROWTH HORMONE-DEPENDENT AND TESTOSTERONE-DEPENDENT REGULATION OF GLUTATHIONE TRANSFERASE SUBUNIT A5 IN RAT-LIVER

The class Alpha glutathione S-transferase (GST) subunit A5 is expresse d in the livers of young male and female rats. After sexual maturation , this protein is no longer detectable in the livers of male rats, but is still expressed in female rats. We have previously demonstrated th at the sexually dimorphic secretion of growth hormone regulates the le vels of certain class Mu GSTs in rat liver, and this study was designe d to investigate the hormonal regulation of GSTA5. Control and hypophy sectomized rats of both sexes were used to study the role of growth ho rmone in the regulation of hepatic GSTA5; and the influence of testost erone on the expression of this same subunit was investigated in intac t females and castrated males. Liver cytosols were subjected to SDS/PA GE and immunoblotting using antibodies directed towards rat (r)GSTAS, and to affinity purification on glutathione-Sepharose followed by reve rse-phase HPLC in order to quantify the relative levels of rGSTA1, A2, A3, A4, M1 and M2 subunits. These analyses revealed that the expressi on of rGSTA5 is, indeed, regulated by both growth hormone and testoste rone.