Perfluorodecanoic acid inactivation of a channel for 2-aminopurine in the L5178Y cell membrane and recovery of the channel

Abstract

Treatment of L5178Y mouse lymphoma cells with perfluoro-n-decanoic acid (PFDA) in growth medium for 24 hr at 30 degrees C produces a dose-dependent inactivation of a channel in the cell membrane. Activity of the channel was estimated from the initial rate of efflux of a fluorescent purine, 2-aminopurine (AP). The L5178Y cells were preloaded with 100 microM AP and excess AP was removed. The preloaded cells were put in a flow system, and AP efflux was estimated continuously at 21 degrees C from the fluorescence emission of AP at 370 nm. The AP channel was markedly inactivated by a treatment with 150 micrograms/ml PFDA for 24 hr at 30 degrees C. There was no significant recovery of AP flux after 3 days at 30 degrees C in fresh growth medium; however, recovery was significant after 6 days. Recovery of activity of the AP channel occurs in 1 day at 37 degrees C. The initial rate of AP efflux for control cells increases with AP concentration; the reaction is not saturated at 1000 microM AP. The efflux of AP was inhibited by the presence of uric acid in the external buffer. An apparent inhibition constant value of 355 microM was determined for urate inhibition of AP efflux. These observations suggest the presence of a urate-sensitive channel for AP in the membrane of L5178Y cells. The channel was inactivated by PFDA under conditions that had no significant effect on cell viability.