Paraquat is known to affect all green plants and other eukaryotic organisms including mammalian cells. The aim of this study was to improve the understanding of paraquat toxicity in nonphotosynthetic plant cells using dark-grown kidney bean cells in tissue culture. It is shown that uptake of paraquat is an active process, and that paraquat inhibits cell growth, reduces DNA synthesis, and inhibits the activity of hydroxypyruvate reductase while enhancing the activity of glutathione reductase which is involved in cellular defense against oxidant stress. Additionally, it is demonstrated that iron ions are involved in paraquat toxicity. We conclude that uptake of paraquat into cells is via polyamine channels and that the deleterious effects of paraquat on these nonphotosynthetic cells are mediated by iron.
