TOXICOKINETICS STUDY OF PARATHION AND ITS METABOLITE PARAOXON IN THE RAT

Although it is generally thought that organophosphorous pesticides do not accumulate in the organism, there are several cases of endogenous reintoxication, cited in the literature, caused by these substances. Among the organophosphorous pesticides, parathion is the agent m ost frequently involved in episodes of acute intoxication, in m any cases with fatal results, and also in occupational toxicology. This article is on its distribution and persistence and includes a biomonitoring and toxicokinetics study of parathion and its principal m etabolite, paraoxon, in male Wistar rats. Gas chromatography is used to calculate parathion and ethyl-paraoxon concentration in blood and different tissues (liver, brain, muscle, and adipose tissue). Parathion's levels decrease gradually with tim e in blood and adipose tissue, whereas in liver, m uscle, and brain parathion's behavior is different; it accumulates until a maximum of concentration is reached at 10 d for brain and m uscle and 16 d for liver. After that parathion's levels begin also to decrease gradually. Paraoxon's behavior is similar to that of its parent compound except in muscle, where its levels decrease gradually with time. Maxim um concentration is reached at 12 d in liver and at 14 d in brain. From the obtained results we propose a tricompartmental model to explain paraoxon and parathion behavior in rat after parathion oral administration.