The Effect of Light on the Toxicity of Paraquat in the Mouse
The paraquat-containing Gramoxone herbicide produces its effect in the simultaneous presence of light and oxygen.
This study aimed at getting a clear picture on the issue of whether light would influence the toxicity of paraquat in mammals.
In the experiment the survival of three groups of Gramoxone treated mice were recorded. The three groups were living in different circumstances for 72 hours: one in constant illumination, one in complete darkness and one in the normal way.
The activities of the peroxide metabolising enzymes, superoxide dismutase (EC 22.214.171.124), catalase (EC 126.96.36.199) and glutathione peroxidase (EC 1.11.19), which have a role in the toxic process, were measured. The value of lipid peroxidation which shows the extent of the membrane damage was also kept under observation.
It was found that illumination heightened the toxic effect of paraquat and membrane destruction increased. The changes of enzyme activity suggest that in the mammalian organism light speeds up the redox cycle of paraquat and consequently increases the quantity of toxic O2−.