Paraquat concentration and renal function in mice fed purified and cereal-based diets

Paraquat, a broad spectrum herbicide, has differential effects in mice depending upon whether a purified or a cereal-based diet is fed. Male ICR mice were fed either a cereal-based closed-formula diet or a purified diet for 7-14 days. After intraperitoneal injection, radiolabeled paraquat was measured in blood, lung, kidney, liver, heart, and urine over a 48-hr period. Accumulation of organic ions was measured in renal tissue slices at 3 hrs after injection of paraquat. Hematocrit, plasma urea nitrogen, and urine volume were measured from 8 to 72 hr after administration of paraquat. From 3 to 12 hr after injection, concentrations of paraquat in plasma, kidney, and liver were greater in mice fed a purified diet than in mice fed a closed-formula diet. Concentration of paraquat in the lung and urine did not differ between dietary groups over a 48-hr period. Three hours after paraquat intake renal tissue organic ion accumulation was higher in mice fed a purified diet. Within 72 hr after paraquat administration plasma urea nitrogen concentration and hematocrit were greater in mice fed a purified diet. Higher tissue concentrations of paraquat in mice fed a purified diet could explain dietary differences previously observed for LD50 and survival time after paraquat injection. While changes in plasma urea and paraquat concentration in the kidney were observed, the effect of a diet-paraquat interaction on renal function was not conclusive, since there was no difference in excretion of paraquat between the dietary groups.