Characterization of tert-butyl alcohol binding to alpha 2u-globulin in F-344 rats

tert-Butyl alcohol (TBA) is widely used in the manufacturing of certain per fumes, cosmetics, drugs, paint removers, methyl tert-butyl ether (MTBE), an d industrial solvents. In both rodents and humans, TBA is a major metabolit e of MTBE, an oxygenated fuel additive. Chronic TBA exposure causes protein droplet nephropathy, alpha 2u-globulin (alpha 2u) accumulation, renal cell proliferation, and with chronic exposure, renal tumors in male, but not fe male, rats. These effects suggest an alpha 2u-mediated mechanism for renal tumors. The objective of the present study was to determine whether TBA or its metabolites bind to alpha 2u. Mature male and female F-344 rats were ad ministered a single gavage dose of 500 mg/kg TBA, 500 mg/kg C-14-TBA, or co rn oil. TBA equivalents/gram or ml of tissue in the male rat kidney, liver, and blood were higher than the levels measured in female rat tissue 12 h a fter C-14-TBA administration. Gel filtration and anion-exchange chromatogra phy demonstrated that C-14-TBA-derived radioactivity co-eluted with alpha 2 u from male kidney cytosol. Protein dialysis studies demonstrated that the interaction between C-14-TBA-derived radioactivity and alpha 2u was reversi ble. Incubations of the low-molecular-weight protein fraction (LMWPF) isola ted from C-14-TBA-treated male rat kidneys with d-limonene oxide (a chemica l with a high affinity to a2u) demonstrated that C-14-TBA-derived radioacti vity was displaced. Gas chromatography-mass spectrometry analysis confirmed that TBA was present in this LMWPF fraction. These results demonstrate tha t TBA interacts with alpha 2u, which explains the accumulation of alpha 2u in the male rat kidney following TBA exposure.