Effect of dietary paraquat on a rat mutant unable to synthesize ascorbic acid.

To obtain some insight into the toxicity of paraquat (PQ) in humans, PQ dichloride at 250 ppm in the diet was administered to both normal (NO) rats and ODS-od/od (OD) rats which are unable to synthesize ascorbic acid (AsA). Firstly, OD rats and NO rats treated with PQ were compared with untreated NO rats (CO). Only OD rats displayed several symptoms of PQ poisoning such as anorexia, hypokinesia, diarrhea, epistaxis, tremor and their pili became rough about 9 days after. Their cysteine proteinase inhibitor level in plasma and lung increased to 2- and 6-fold, respectively, of CO. In contrast, NO rats treated with PQ resembled CO rats, and their cysteine proteinase inhibitor levels were unchanged until 11 days. After this period they began to display symptoms. Secondly, OD rats fed with different amounts of AsA were compared. Excess AsA delayed the onset of symptoms by only 1 day. Thirdly, the day of onset of symptoms was found to be influenced with the weight of rats.