ABSTRACT
Aerobic organisms continuously produce reactive oxygen species (ROS) during metabolism and eliminate these toxic substances through a very ancient antioxidant defense system. However, many chemicals can either potentiate ROS production through interactions with the systems that normally produce ROS at low levels, or by catalyzing and participating in some ROS-producing reactions. Other chemicals can impair antioxidant defenses, rendering cells more susceptible to oxidative damage. The presence of oxidative stress is commonly investigated in fi sh in biomonitoring and laboratory studies, since this process has a great effect on fi sh health.
