Competition between paraquat and putrescine for accumulation by rat lung slices

Slices from rat lungs actively accumulate both paraquat and putrescine, while endogenous polyamines inhibit the accumulation of each. The organic ions phenol red and tetraethylammonium, as well as cycloleucine, have little, if any, effect on either paraquat or putrescine transport. Double reciprocal plots indicate that paraquat and putrescine compete for the same transport system in lung slices. The affinity for the system is much greater for putrescine than for paraquat; thus, a transport system normally meant for accumulation of polyamines can be usurped by the exogenous compound paraquat. Furthermore, these data support the hypothesis that paraquat and putrescine are accumulated by the same cell type.