The effect of high and low dosages of paraoxon in β-naphthoflavone-treated rats

✍ Scribed by Watson, Angela M. ;Chambers, Janice E.

• Publisher: John Wiley and Sons
• Year: 1996
• Tongue: English
• Weight: 141 KB
• Volume: 11
• Category: Article
• ISSN: 0887-2082
• DOI: 10.1002/(sici)1522-7146(1996)11:6<263::aid-jbt1>3.0.co;2-i

✦ Synopsis

Aliesterases (carboxylesterases) are serine esterases that can serve a protective role for the target acetylcholinesterase (AChE) during organophosphorus insecticide intoxication because the former esterases are alternate phosphorylation sites. The levels of aliesterase activity in liver and plasma and AChE activity in brain regions were investigated after the intravenous administration of paraoxon (PO) into female rats. The rats were pretreated intraperitoneally with b-naphthoflavone (BNF), which decreases hepatic aliesterase activity following a 3 day in vivo treatment, and/or tri-o-tolyl phosphate (TOTP) to inhibit aliesterases. The liver aliesterases were inhibited less by PO in BNF-treated rats than in control rats, which suggests that either BNF exposure may have resulted in aliesterases that are less sensitive to PO inhibition or BNF may have altered PO's availability. The BNF treatment did not seem to alter the degree of inhibition of the brain AChE activity following the low dosage of paraoxon (0.04 mg/kg). However, the brain AChE activity in the PO/TOTP/BNF-treated rats was lower than that in the PO/TOTP-treated rats, suggesting that BNF also caused changes in systems affecting the disposition of PO in addition to the changes in the hepatic aliesterases. At the high dosage of paraoxon (0.12 mg/kg), the AChE and aliesterase activities showed a pattern similar to that of the low dosage. This suggests that the aliesterases, as altered by BNF exposure, even when nearly completely inhibited, did not alter the response of the target enzyme, AChE, and, therefore, the magnitude of the toxic response. ᭧ 1997