GLUTATHIONE CONJUGATES OF TERT-BUTYL-HYDROQUINONE, A METABOLITE OF THE URINARY-TRACT TUMOR PROMOTER 3-TERT-BUTYL-HYDROXYANISOLE, ARE TOXIC TO KIDNEY AND BLADDER

3-tert-Butyl-4-hydroxyanisole and tert-butyl-hydroquinone (TBHQ) are a ntioxidants known to promote renal and bladder carcinogenesis in the r at, although the mechanisms of these effects are unclear. Because glut athione (GSH) conjugates of a variety of hydroquinones are nephrotoxic , and because 2-tert-butyl-5-(glutathion-S-yl)hydroquinone [5-(GSyl)TB HQ], 2-tert-butyl-6-(glutathion-S-yl)hydroquinone [6-(GSyl)TBHQ], and 2-tert-butyl-3,6-bis-(glutathion-S-yl)hydroquinone [3,6-bis-(GSyl)TBHQ ] have been identified recently as metabolites of TBHQ in the male rat , we investigated the effects of these metabolites in the male rat. At the highest dose tested (400 mu mol/kg, i.v.) 5-(GSyl)TBHQ and 6-(GSy l)TBHQ caused 2-fold increases in the urinary excretion of gamma-gluta mgl transpeptidase and alkaline phosphatase, and pigments arising from the polymerization of metabolites were deposited in the kidney. 3,6-b is-(GSyl)TBHQ (200 mu mol/kg) was the most potent of the GSH conjugate s tested and produced significant increases in the urinary excretion o f gamma-glutamyl transpeptidase, alkaline phosphatase, lactate dehydro genase, and glucose (2-, 2-, 22-, and 11-fold increases, respectively) . Alterations in the biochemical parameters correlated with the degree of single cell and tubular necrosis in the S-3-M segment of the proxi mal tubule, as observed by light microscopy. In addition to nephrotoxi city, 3,6-bis-(GSyl)TBHQ increased the bladder wet weight 2-fold and c aused severe hemorrhaging of the bladder. The half-wave oxidation pote ntials of 5-(GSyl)TBHQ and 6-(GSyl)TBHQ were similar to that of TBHQ, whereas the half-wave oxidation potential of 3,6-bis-(GSyl)TBHQ was si milar to 100 mV higher than that of TBHQ. The TBHQ-GSH conjugates also catalyzed the formation of 8-hydroxydeoxyguanosine, indicating that G SH conjugation does not impair the redox activity of TBHQ. Because som e chemicals may induce carcinogenesis by a mechanism involving cytotox icity followed by sustained regenerative hyperplasia, our results sugg est that the toxicity of GSH conjugates of TBHQ to kidney and bladder may contribute to the promoting effect of 3-tert-butyl-4-hydroxyanisol e and TBHQ in these tissues.