 the production of reactive oxygen species on addition of hexavalent chromium ( potassium dichromate , k2cr2o7 ) to lung cells in culture was studied using flow cytometer analysis . 
 a coulter epics profile ii flow cytometer was used to detect the formation of reactive oxygen species after k2cr2o7 was added to a549 cells grown to confluence . 
 the cells were loaded with the dye , 2',7'-dichlorofluorescein diacetate , after which cellular esterases removed the acetate groups and the dye was trapped intracellularly . 
 reactive oxygen species oxidized the dye , with resultant fluorescence . increased doses of cr(vi ) caused increasing fluorescence ( 10-fold higher than background at 200 microm ) . 
 addition of cr(iii ) compounds , as the picolinate or chloride , caused no increased fluorescence . 
 electron paramagnetic resonance ( epr ) spectroscopic studies indicated that three ( as yet unidentified ) spectral " signals " of the free radical type were formed on addition of 20 , 50 , 100 , and 200 microm cr(vi ) to the a549 cells in suspension . 
 two other epr " signals " with the characteristics of cr(v ) entities were seen at field values lower than the standard free radical value . 
 liver microsomes from male sprague - dawley rats treated intraperitoneally with k2cr2o7 ( 130 mumole / kg every 48 hr for six treatments ) had decreased activity of cytochromes p4503a1 and/or 3a2 , and 2c11 . 
 hepatic microsomes from treated female sprague - dawley rats , in contrast , had increased activities of these isozymes . 
 lung microsomes from male sprague - dawley rats had increased activity of p4502c11.imagesfigure 4.figure 6 . 
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