Figure 6.

Effect of paraquat on DA and BH₄ pathways. Adult Drosophila heads that were 24 h posteclosion at the initiation of paraquat feeding were homogenized in perchloric acid, and pteridine and DA pathway metabolites were separated by HPLC. A, l-DOPA pools increase in male and female heads, indicating that TH activity is stimulated by paraquat. ^# p < 0.05. B, DA pools diminish over 24 h of exposure to 20 mm paraquat. ^# p < 0.05. C, DOPAC levels increase during paraquat exposure, showing that the loss of DA is attributable to its oxidation during paraquat exposure. D, BH₄ pools also decrease in response to paraquat. E, Biopterin pools increase during exposure, demonstrating that at least part of the loss of BH₄ is attributable to its oxidation. Each mean value is the average of six replications, and each replication was obtained from an extract of 75–100 heads. Error bars indicate SEM. *p < 0.05, significant difference; **p < 0.01, significant difference. M, Male; F, female.