Nephrotoxicity of paraquat in the sheep and the associated reduction in paraquat secretion.

Paraquat was administered to sheep at doses of 1, 2, 4, and 8 mg/kg. Paraquat was nephrotoxic to sheep, producing glomerular and tubular defects. Glomerular filtration rate (GFR) fell in a dose-dependent manner. Secretion of paraquat into the tubule was inhibited at low doses prior to any influence of paraquat on GFR. Subsequently, GFR and paraquat clearance (ClPQ) fell in parallel. Inhibition of paraquat secretion by paraquat itself was dose dependent. Poisoning of the secretory component removed a large part of the excretory capacity for paraquat.