Abstract

The purpose of this study is to investigate the relationship between ATP levels in human natural killer (NK) cells and their cytotoxic function. NK cells are a subset of lymphocytes that act as primary defense against tumor cells and virally infected cells. NK cells were exposed to various concentrations of rotenone (RO), oligomycin (OL), and tributyltin (TBT) for various lengths of time before determining the levels of ATP (using a chemiluminescent assay) and cytotoxic function (determined by a chromium release assay). RO inhibits ATP production at Complex I, while OL inhibits ATP synthase. TBT is an environmental contaminant and has been detected in human blood. A 1 h exposure to either 0.5 μM RO or OL reduced ATP levels by about 20% but did not have any measurable effect on cytotoxic function. Both 24 h and 48 h exposures to these compounds caused a 20–25% reduction in ATP levels. Cytotoxic function was reduced by about 50% after 24 h or 48 h exposures to 0.5 μM RO. A 24 h exposure to 0.5 μM OL reduced cytotoxic function by about 50%, while a 48 h exposure reduced it by about 75%. It was observed that concentrations of 10, 25, 50, and 100 nM TBT did not significantly reduce ATP levels after 24 h, however they caused significant decreases in cytotoxic function. Cell viability was not affected by exposure to these compounds as determined by trypan blue exclusion. The results of this study indicate that decreased ATP levels may lead to decreased NK cytotoxic function but there is no absolute association. They also indicate that TBT-induced decreases in NK cytotoxic function cannot be attributed to TBT-induced decreases in ATP levels alone. Supported by NIH grant 2S06GM08092-28

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