Effect of cations and some compounds on paraquat accumulation into cultured pneumocytes.

Paraquat and diquat, bipyridilium herbicides, have been shown to be accumulated into pneumocytes of three species in culture. Paraquat at 10(-3) M was accumulated to a maximum of 3-7 nmol/mg protein for 20 min. Diquat accumulated more slowly but reached a concentration of 1-6 nmol/mg protein for 60 min. Differences in the ability of various pneumocytes to accumulate paraquat and diquat appear to exist. It was found that the cations, Ca++, Na+ and K+, reduced the accumulation of paraquat. Valinomycin stimulated paraquat accumulation significantly. On the other hand, paraquat accumulation was inhibited by 2, 4-dinitrophenol. These results indicate that paraquat may be accumulated, in part, as cation species into pneumocytes and also by a energy-dependent process regulated by cellular ATP.