Time-dependent and tissue-specific variations of glutathione transferase activity during gestation in the mouse

Glutathione transferases (GSTs; EC. 2.1.5.18) activity was measured in maternal liver and conceptal tissues during gestation. In maternal liver, maximum activity was found at gestational day (GD) 9 after which it slowly decreased up to the end of gestation. The placental GSTs activity at GD18 was three times lower than that found at GD14. Conversely, fetal liver GSTs at GD14 was about 75% that at GD18. It was also observed that GSTs activity at GD9 and GD10 was higher in visceral yolk sac than in embryo proper. Substrate specificity measurements, SDS PAGE analysis and HPLC runs, carried out on GSH-affinity purified fractions, revealed that with the progress of gestation in maternal liver an increase in pi class GSTs subunit occurs, with a concomitant decrease in alpha class GSTs. With respect to the time of gestation, a significant change in alpha, mu and pi class GSTs expression also occurred in fetal liver and in chorioallantoic placenta. It was concluded that during gestation the GSTs system is subjected to a time-dependent and tissue-specific modulation which may play a protective role against developmental toxicants.