Free malondialdehyde levels in the urine of rats intoxicated with paraquat.

We examined the excretion of free malondialdehyde (MDA) in the urine of rats to which a herbicide, Gramoxone, had been orally administered. The herbicide was administered for 2 days at a dose of 60 mg paraquat/kg body weight/day. As a result, the concentration of free MDA decreased following the intake of Gramoxone. The total amount of free MDA increased temporarily, but then it decreased significantly to below normal values. Rats that died during this experimental period did not excrete any free MDA. In the surviving animals, the MDA concentration in serum and lung microsomes decreased, while that in liver microsomes increased slightly after intake of the poison. Although the cause of the decrease in the urinary free MDA level remains unclear, the marked changes may provide valuable information regarding a toxic mechanism of paraquat intake.