Protein Adducts of Pentachlorophenol Metabolites
Chem. Res. Toxicol., Vol. 9, No. 3, 1996 653
Protein adducts of any semiquinone species have not
been reported to our knowledge. We have characterized
(2) McConnel, E. E. (1989) Toxicology and carcinogenesis studies of
two pentachlorophenol technical-grade mixtures in B6C3F1 mice,
U. S. National Toxicology Program. Department of Health and
Human Services, NIH publication No. 89-2804.
(3) McConnel, E., Huff, J . E., Hejtmancik, M., Peters, A. C., and
Persing, R. (1991) Toxicology and carcinogenesis studies of two
grades of pentachlorophenol in B6C3F1 mice. Fundam. Appl.
Toxicol. 17, 519-532.
the adducts formed by the reaction of Cl
,4-SQ with protein sulfhydryl groups in vivo. In both
Alb and Hb, levels of adducts derived from the quinone
species Cl -1,4-BQ (either as Cl BQ-Y or as combined
multisubstituted adducts) were greater than those de-
rived from the corresponding semiquinone species Cl
4 4
-1,2-SQ and Cl -
1
4
3
(
(
(
4) Ahlborg, U. G., Larsson, K., and Thunberg, T. (1978) Metabolism
of pentachlorophenol in vivo and in vitro. Arch. Toxicol. 40, 45-
53.
5) J uhl, U., Witte, I., and Butte, W. (1985) Metabolism of pentachlo-
rophenol to tetrachlorohydroquinone by human liver homogenate.
Bull. Environ. Contam. Toxicol. 35, 596-601.
4
-
1
,4-SQ (Table 3).
4
Even though no adducts of Cl -1,2-BQ were detected
in the blood of rats to which PCP had been administered,
adducts of Cl -1,2-SQ were detected in both Hb and Alb.
4
6) Ahlborg, U. G., Lindgren, J . E., and Mercier, M. (1974) Metabo-
lism of pentachlorophenol. Arch. Toxicol. 32, 271-281.
In Hb, the levels of Cl
higher than those of Cl
4
-1,2-SQ-Y were about 2.4-fold
-1,4-SQ-Y, whereas in Alb the
(7) J acobson, I., and Yllner, S. (1971) Metabolism of 14C-pentachlo-
4
rophenol in the mouse. Acta Pharmacol. Toxicol. 29, 513-524.
levels of both types of adducts were similar (Table 3).
Regarding preferential reactions of semiquinones be-
(
8) Edgerton, T. R., Moseman, R. F., Linder, R. E., and Wright, L.
H. (1979) Multi-residue method for the determination of chlori-
nated phenol metabolites in urine. J . Chromatogr. 170, 331-342.
tween the two proteins, the levels of Cl
4
-1,2-SQ-Y and
Cl -1,4-SQ-Y were about 3.4- and 1.5-fold higher, respec-
4
(9) Reigner, B., Rigod, J . F., and Tozer, T. (1990) Simultaneous assay
of pentachlorophenol and its metabolite, tetrachlorohydroquinone,
by gas chromatography without derivatization. J .Chromatogr.
tively, in Hb than in Alb. This is in contrast to what
was observed in vivo for the quinone adducts, especially
Cl BQ-Y, where Alb adducts were 2.5-fold higher than
3
the Hb adducts. These observations suggest that either
semiquinone species were more readily transported into
the erythrocyte than were their quinone analogues or
that semiquinone radicals were formed within the eryth-
rocyte per se.
5
33, 111-124.
(
10) Witte, I., J uhl, U., and Butte, W. (1985) DNA-damaging properties
and cytotoxicity in human fibroblasts of tetrachlorohydroquinone,
a pentachlorophenol metabolite. Mutat. Res. 145, 71-75.
11) Gause, E. M., Montalvo, D. A., and Rowlands, J . R. (1967) Electron
spin resonance studies of the chloranil-cysteine, dichlone-cysteine
and dichlone-glutathione reactions. Biochim. Biophys. Acta 141,
(
2
17-219.
The protein adducts measured in this investigation
displayed evidence of biphasic elimination in vivo with
a rapid phase ending within 48 h of administration of
PCP and a much slower terminal phase, which was more
pronounced in Hb than in Alb (see Figure 9). Using the
time points between 24 and 336 h following administra-
tion of PCP, we estimated that the half-times for elimi-
nation of the monosubstituted Hb and Alb adducts were
about 155 h and 41 h, respectively. For Hb, this terminal
elimination half-time (155 h) was significantly shorter
than that anticipated from the normal rate of erythrocyte
turnover in the rat, which is 60 days (22). Regarding
Alb, the estimated half-time (41 h) is slightly shorter than
the rate of turnover of serum Alb in the rat, which is
reported to be 2-3 days (23). In either case, the data
suggest that the adducts are somewhat unstable in vivo,
probably due to continued reactions with sulfhydryl
groups.
In general, the mechanisms most frequently invoked
to explain quinone-mediated toxicities involve either
sulfhydryl arylation or oxidative stress as a consequence
of redox cycling. Recently, the potential importance of
quinone-induced protein cross links has also been ad-
dressed . For example, the neurotoxicity of 6-hydroxy-
dopamine and 5,6-dihydroxytryptamine is thought to
arise, at least in part, from extensive protein cross-linking
(12) Den Besten, C., van Bladeren, P. J ., Duizer, E., Vervoort, J ., and
Rietjens, I. M. C. M. (1993) Cytochrome P450-mediated oxidation
of pentafluorophenol to tetrafluorobenzoquinone as the primary
reaction product. Chem. Res. Toxicol. 6, 674-680.
(
13) Van Ommen, B., Adang, A., Muller, F., and van Bladeren, P. J .
(1986) The microsomal metabolism of pentachlorophenol and its
covalent binding to protein and DNA. Chem.-Biol. Interact. 60,
1
-11.
(
14) Waidyanatha, S., McDonald, T. A., Lin, P-H., and Rappaport, S.
M. (1994) Measurement of hemoglobin and albumin adducts of
tetrachlorobenzoquinone. Chem. Res. Toxicol. 7, 463-468.
(15) Van Ommen, B., Adang, A. E. P., Brader, F., Posthumus, M. A.,
Muller F., and van Bladeren, P. J . (1986) The microsomal
metabolism of hexachlorobenzene: Origin of the covalent binding
to protein. Biochem. Pharmacol. 35, 3233-3238.
(
16) Pathak, D. N., Levay, G., Pongracz, K., and Bodell, W. J . (1994)
3
2
Identification and P-postlabelling detection of DNA adducts in
the bone marrow and white blood cells of B6C3F1 mice treated
with benzene (Abstract). In: Proceedings of AACR Special
Conference-Risk Assesment in Environmental Carcinogenesis,
Whistler, British Columbia, Canada. Philadelphia, PA, American
Association for Cancer Research, 1994.
(17) Ting, D., Smith, M. T., Doane-Setzer, P., and Rappaport, S. M.
(1990) Analysis of styrene oxide-globin adducts based upon
reaction with Raney nickel. Carcinogenesis 11, 755-760.
18) Rettig, V. G. and Latscha, H. P. (1980) Reaktionen von Antimon-
(V)-chlorid mit Hydrochinon. Chem.-Ztg. 104, 13-14.
(
(19) Ringler, D. H., and Dabich, L. (1979) Hematology and Clinical
Biochemistry. In The Laboratory Rat, Volume 1 Biology and
Diseases (Baker, H. J ., Lindsey, J . R., and Weisbroth, S. H., Eds.)
Academic Press, New York.
(
20) Rappaport, S. M., Ting, D., J in, Z., Yeowell-O’Connell, K.,
Waidyanatha, S., and McDonald, T. (1993) Application of Raney
nickel to measure adducts of styrene oxide with hemoglobin and
albumin. Chem. Res. Toxicol. 6, 238-244.
(24). Although our assay cannot differentiate adducts
arising from protein-protein cross links from those of
proteins and nonprotein thiols, our results are certainly
consistent with the notion that protein-protein cross
(
21) McDonald, T. A., Waidyanatha, S., and Rappaport, S. M. (1993)
Measurement of adducts of benzoquinone with hemoglobin and
albumin. Carcinogenesis 14, 1927-1932.
links are formed. Hence, our observation that Cl
4
-1,4-
BQ forms multisubstituted adducts leads us to speculate
that protein-protein cross links might play a role in the
toxicity of PCP.
(22) Derelanko, M. J . (1987) Determination of erythrocyte life span
in F344, Wistar, and Sprague-Dawley rats using a modification
3
3
of the [ H]diisopropylfluorophosphate ([ H]DFP) method. Fun-
dam. Appl. Toxicol. 9, 271-276.
(
23) Schreiber, G., Urban, J ., Z a¨ hringer, J ., Reutter, W., and Frosch,
U. (1970) The secretion of serum protein and the synthesis of
albumin and total protein in regenerating rat liver. J . Biol. Chem.
Ack n ow led gm en t. This work was supported by the
National Institute of Environmental Health Sciences
through Grant P42ES05948.
2
5, 4531-4538.
(
24) Rotman, A., Daly, J . W., and Creveling, C. R. (1976) Oxygen-
dependent reaction of 6-hydroxy-dopamine, 5,6-dihydroxytry-
ptamine and related compounds with proteins in vitro: a model
for cytotoxicity. Mol. Pharmacol. 12, 887-891.
Refer en ces
(
1) Kutz, F. W., and Cook, B. T. (1992) Selected pesticide residues
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population. J . Toxicol. Environ. Health 37, 277-291.
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