Bioavailability in rats of bound pesticide residues from tolerant or susceptible varieties of soybean and canola treated with metribuzin or atrazine

Abstract

Susceptible or tolerant varieties of soybean treated with metribuzin, or canola treated with atrazine were grown in a controlled environment. Shoots and fruits were harvested at maturity and extracted exhaustively with methanol. The extracted materials containing bound 14C residues were subsequently fed to rats for two days. The elimination of 14C in urine and feces was monitored for 4 days and the distribution of radioactivity in liver, kidney and heart was studied. Higher 14C residues in urine were present in animals fed fruits compared to shoots of soybean or canola of both susceptible and tolerant varieties. The bound atrazine residues from the pods of Atr Tower (tolerant variety of canola) were more bioavailable than Tower (susceptible variety of canola). Bioavailability of bound atrazine from the shoots of canola in both varieties was very low. In soybean fed animals, bound metribuzin derived 14C from the susceptible variety (Maple Amber) was more bioavailable than from the resistant variety (Maple Arrow). However, feeding the animals with susceptible or tolerant varieties of soybean or canola containing bound residues of 14C metribuzin or 14C atrazine for two days did not result in the accumulation of radioactivity in the body organs studied. Thus our data show that the bioavailability of these bound pesticides was dependent on the type of plant parts ingested and the variety of plant species.