Dose-dependent inhibition of phospholipase A2 by paraoxon in vitro: Preliminary results

✍ Scribed by G. Petroianu; U. Helfrich; A. Schmitt; W. Bergler; R. Rüfer

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 52 KB
• Volume: 17
• Category: Article
• ISSN: 0260-437X
• DOI: 10.1002/(sici)1099-1263(199711/12)17:6<421::aid-jat468>3.0.co;2-f

✦ Synopsis

To establish the dose dependency of phospholipase A 2 (PLA 2 ) inhibition by the organophosphorus compound (OPC) paraoxon (POX), human platelet membranes were incubated after Ca 2+ removal (to inactivate the PLA 2 ) with 0.3, 1 and 3 g ml ؊1 POX for 5, 30 and 60 min each. The PLA 2 activity (pmol mg ؊1 protein min ؊1 ) was measured after subsequent enzyme reactivation. The PLA 2 activity in native platelets was considered to be 100%; all other measured values are expressed as a percentage thereof. Data were analysed with the Mann-Whitney Wilcoxon rank order test and ANOVA. Statistical significance was assumed for P р р р 0.01. Paraoxon inhibited in a dose-dependent manner the PLA 2 activity. Different incubation times of the inactive PLA 2 with POX did not have any additional effect on the activity reduction after activation. At the tested POX concentrations the PLA 2 activity was 42 ؎ 5.4%, 29 ؎ 3.4% and 15 ؎ 6.6%, respectively. The corresponding butyrylcholine esterase (BChE) activities were 1% of the baseline activity. Phospholipase A 2 is less sensitive to POX inhibition than BChE and, at clinically achievable POX concentrations, shows a clear dose dependency. Further work is needed to elucidate the exact mechanism and time dependency of the phenomenon.