Expression of quinone reductase activity in embryonal and adult porcine tissues

Quinone reductase (QR; EC 1.6.99.2) is recognized as a major antimutagenic/anticarcinogenic enzyme in the organism. Our recent studies demonstrated the presence of significant QR activity in the early human placenta; whether this enzyme is expressed by the mammalian embryo is not known at present. In the investigation reported here, we sought to determine whether or not QR activity is detected in porcine embryonal tissues and if so, how early this expression takes place. In addition, the enzyme activity in the embryo was compared to that present in adult porcine tissue. Enzyme activity was determined by a colorimetric method with menadione as substrate in the presence of tetrazolium salt (MTT). NADH was a preferable cofactor in the embryo, whereas in the adult tissues NADPH was a better cofactor. Results show that the enzyme is present in all the embryonal organs tested from a very early age (30 days of gestation). Among the organs tested, activity was highest in the porcine embryo liver, and the specific activity remained unchanged until Day 70. Activity in the embryonal kidney increased with advancing gestation. The enzyme activity in embryonal tissues was much lower than that measured in the adult liver (30-40-fold). These findings suggest that the embryo has the potential for inactivating carcinogens/mutagens that will subsequently be eliminated by the maternal organism, thus protecting against adverse environmental impacts during the most critical period of development.