Bioavailability to rat and toxicity of bound 14 C - pirimiphos-methyl residues in stored soybeans

ABSTRACT

The amount of bound residues of 14C-pirimiphos-methyl in stored soybeans was determined to examine their bioavailability and toxicological potential in the experimental animals. Whole seeds of soybeans were treated with 14C-pirimiphos-methyl insecticides at a dose of 30 mg/kg and stored for 24 weeks. The level of total internal and bound insecticide residues represented 60% and 4-5% of the actual dose, respectively. Feeding rats with the soybeans-bound residues for 72 hours, revealed that these residues were bioavailable. The main excretion route was the urine [40%] and feces [108%], while a small amount [6%] could be detected in the expired air. About 25% of the administered radioactivity was detected among various organs of the rat. Chromatographic analysis of urine showed the presence of some free as well as conjugated metabolites of pirimiphos-methyl. Subchronic feeding experiments on mice for 90 days with a diet containing the bound pesticide residues at a dose of 1.6 ppm/day/mouse caused no significant symptoms of toxicity during the period of the experiment. Both plasma and erythrocyte cholinesterases suffered a slight inhibition during the first 15 days. The blood picture and liver function enzymes showed no significant differences from control values. A significant increase in the level of blood urea nitrogen was observed; Whereas, creatinine clearance showed only a slight increase as compared with controls