Immunohistochemical localization and dynamics of paraquat in small intestine, liver and kidney.

Immunohistochemical techniques were used to observe the localization of paraquat in the small intestine, liver and kidney, organs that absorb and eliminate chemicals. Paraquat-poisoned rats were killed 3 h, 12 h, 24 h, 3 days, 7 days and 10 days after intravenous administration of paraquat. Three hours after injection, paraquat was localized in hepatocytes and in the kidney in the epithelial cells of the distal tubule. The amount of paraquat in the liver and kidney increased by 24 h after the administration and thereafter decreased with time, suggesting that paraquat is secreted into bile and urine. In the intestine, 3 h after injection, paraquat was localized in the epithelial cells. The same finding was also made in rats with a cannulated bile duct. Therefore, it is likely that paraquat is secreted into the gut lumen from epithelial cells and that paraquat secreted from liver into the duodenum is reabsorbed into the epithelial cells of the intestine.