The effect of carbohydrate sulfate salts on the absorption and excretion of the herbicide, paraquat dichloride (PQ), was investigated in rats. A mixture of PQ and sodium dextran sulfate (DS) or sodium glucose sulfate (GS) was given orally to rats and then feces and urine were collected daily for 14 d. The cumulative amount of PQ excreted in the feces of rats given the mixture PQ and DS, or PQ and GS was 82.6% and 76.7% respectively. When PQ alone was administered, 56.7% was excreted in feces. Most (nearly 90%) of the PQ detected in feces was excreted within the first 24 h of the 14 d period in each case. The cumulative amount of PQ excreted in the urine over the 14 d period was 1.2% for the mixture PQ and DS and 0.7% for the mixture PQ and GS. When PQ was given alone the corresponding figure was 7.2%. In addition, the effect of DS and GS on PQ absorption from the rat small intestine was investigated using an in situ recirculating perfusion method. During 180 min period of recirculating perfusion, using PQ alone in normal saline, 13.4% of the herbicide was absorbed from the intestine. However, when the mixture of PQ and DS (or PQ and GS) in saline was used, the absorption was 3.9% for PQ-DS, of 4.8% for PQ-GS. Furthermore, an association of PQ with DS, or GS, was observed using gel filtration of the mixture of PQ-DS and PQ-GS in saline solution.(ABSTRACT TRUNCATED AT 250 WORDS)