Bioavailability and biological activity of wheat-bound chlorpyrifos-methyl residues in rats.

Wheat grain was treated with 14C-chlorpyrifos-methyl to generate bound residues for determining their bioavailability to rats. In a parallel experiment, bound residues were prepared with non-labelled chlorpyrifos-methyl to determine possible adverse effects in rats fed the grain-bound residue for 28 and 90 days. Two dose levels of 10 and 50 ppm were initially used on the grain. The 10 ppm led to the formation of 25.1% bound residues (2.51 ppm) after 6 months as determined by radiomeasurement. The higher dose was assumed to form 12.55 ppm bound residues. When 14C-bound residues were fed to male rats for 24 hours, the animals eliminated 75% of the radioactivity in urine, 7% in expired air and 8% in faeces after 3 days, indicating that the bound residues were highly bioavailable. A further "bioavailable" amount (4%) was found in selected organs.

Toxic effects of bound malathion residues in rats.

The level of bound malathion residues in treated wheat grain and its toxic effects on rats were investigated. Wheat grain was treated with [14C] malathion (specific activity: 2.76 MBq/mg) to determine the bioavailability of bound residues in rats. At the same time, grain was treated with nonlabeled malathion to test for possible toxic effects of bound residues in a subchronic (90 days) feeding study in rats at two dose levels, 10 and 100 ppm. It was observed that the level of malathion-bound residues amounted to 11.28% of the applied dose (for six months). Also, it was noted that the main route of [14C]-malathion excretion was through the urine. This signifies that grain-bound malathion was bioavailable. In subchronic test on rats bound malathion residues (both dose levels) induced effects to some extent in organ weight (spleen and adrenals), and blood ChE activity. In both, males and females, there was an increase in SGPT activity (lower dose), and in alkaline phosphatase in females (higher dose). Hematological data showed changes only in hemoglobin concentration in males (both dose levels).

Toxic effects of pirimiphos-methyl residues on rats.

This study analyzes the level of total and bound pirimiphos-methyl residues in treated wheat grain and its toxic effects on rats. Wheat grain was treated with [14C]pirimiphos-methyl of 16.36 mCi/mmol specific activity to determine the bioavailability of bound residues in rats. At the same time, grain was treated with nonlabeled pirimiphos-methyl as required to determine any possible toxic effects of bound residues in a subacute feeding study in rats. Two dose levels were used: 10 and 100 ppm (the former being the recommended dose level in practical treatment). Estimation of the type of residues was performed at intervals of 0, 30, 90, 120, 150, and 180 days. During and after the animal feeding study, changes in body weight gain, organ weight, cholinesterase activity, serum enzyme activity, and hematology were investigated. There is an indication that bound residues of the pesticide pirimiphos-methyl provoke toxic effects to some extent.

The effect of banol and paraoxon on the NADPH-cytochrome c reductase activity and cytochrome P-450 content in rats.

We investigated the effect of banol and paraoxon on the activity of NADPH-cytochrome c reductase and cytochrome P-450 concentration in microsomes of rats treated in vivo with these compounds alone, or in the presence of phenobarbitone. The results showed that banol reduced the NADPH-cytochrome c reductase activity and the concentration of cytochrome P-450, while paraoxon reduced the activity of NADPH-cytochrome c reductase, but increased the cytochrome P-450 concentration. Phenobarbitone stimulated an increased NADPH-cytochrome c reductase activity and cytochrome P-450 concentration. When applied with banol and paraoxon, phenobarbitone lowered their inhibitory effect.