Hydroquinone sebabkan barah!
The available studies on the
carcinogenicity of hydroquinone
are summarized in Table 17.
7.7.1 Long-term bioassays
In an NTP study (NTP, 1989; Kari et al., 1992), groups of 65
F-344/N rats of each sex were given
hydroquinone (0, 25 or 50 mg/kg
body weight) in deionized water by gavage 5
days/week for up to 103
weeks, and groups of 65 B6C3F1
mice of each sex were administered
0, 50 or 100 mg/kg body weight according to
the same schedule. A
15-month interim kill of ten animals from
each group showed that the
kidney of male rats was a target organ forthe toxicity (see also
section 7.4), since there was a
compound-related increased severity
of nephropathy. The lesions were less
severe in female rats, in
which a mild regenerative anaemia was also
found (slightly decreased
haematocrit, haemoglobin and erythrocyte
count). After termination
of the experiment, a dose-related increase
in the incidence of renal
tubular cell adenomas was observed in male
rats (controls 0/55, low
dose 4/55, high dose 8/55; P = 0.003). The
incidence of adenomas was
closely associated with the severity of
chronic nephropathy. No
renal adenomas were observed in animals
examined at 15 months, when
the severity of nephropathy was less
severe, or in female rats,
which developed nephropathy to a lesser
degree. In the male rats,
9/12 adenomas were seen in kidneys with
marked nephropathy, two were
seen in animals with moderate nephropathy,
and only one was seen in
an animal with mild nephropathy. In the
high-dose group single
tubules exhibited tubular cell hyperplasia.
No renal tumours were
seen in females. A dose-related increase in
the incidence of
mononuclear cell leukaemia was found in
female rats (controls 9/55,
low dose 15/55, high dose 22/55) (P <
0.01 in the high-dose group
versus controls). However, this was not
observed in the animals
killed at 15 months. The incidence in
controls was lower than the
historical control mean incidence but was
within the historical
control group range.
Table 17.
Carcinogenicity studies in animals
Species
Route of Number of
Dosage Time of Result Remarks Reference
exposure animals treatment
Long-term bioassays
Mouse
oral 64 or 65 of 50 or 100 103 weeks liver lesions (males), some evidence of NTP (1989);
each sex mg/kg hepatocellular
adenomas carcinogenic activity Kari et al.
per group 5 days/week (females) for female mice (1992)
Mouse
oral 30 m, 30 f 0.8% in 96 weeks squamous cell hyperplasia of potential of Shibata et al.
the
diet the
forestomach epithelium; hepatocarcinogenicity (1991)
renal tubular hyperplasia and
in male mice
adenomas (males); increased
incidence
of liver foci and
hepatocellular adenomas
(males)
Rat
oral 65 of each 25 or 50 103 weeks nephropathy (more severe in some evidence of NTP (1989);
sex per mg/kg males), renal
tubular cell carcinogenic
activity Kari et al.
group 5 days/week hyperplasia and
adenomas for male and female (1992)
(males), leukaemia (females)
rats
Rat
oral 30 m, 30 f 0.8% in 104 weeks renal tubular hyperplasia, potential of renal Shibata et al.
the
diet adenomas and
epithelial carcinogencity
in (1991)
hyperplasia of the renal
male rats
papilla (males); decreased
incidence of liver foci
Table 17. (contd).
Species
Route of Number of Dosage Time of Result Remarks Reference
exposure animals treatment
Carcinogenicity-related studies
Mouse
skin 24 m 0.3 ml of 6.7% one skin papilloma (1/24) no initiating Roe & Salaman
application solution; application;
activity (1955)
0.3 ml
of then three
0.5%
croton weeks later,
oil 18 weekly
applications
Mouse
skin 50 f 5 mg three 368 days papilloma (7/50), squamous no co-carcinogenic van Duuren &
application times
carcinoma (3/50)
or tumour-promoting Goldschmidt
weeklya
activity; partial
(1976)
inhibition of BP
carcinogenicity
Mouse
implantation not stated 2 mg 25 weeks carcinomas (6/19) Boyland
et al.
in urinary
(1964)
bladder
Rat
oral 20 f 0.8% in 32 weeks no preneoplastic lesions Kurata et al.
basal
dietb or
papillomas of the (1990)
urinary bladder
Rat
oral 15-16 m 0.8% in 51 weeks no increase in forestomach or Hirose et al.
dietc
glandular stomach neoplasms (1989)
Rat
oral 5 m 8 weeks
no proliferative changes Shibata et al.
in forestomach or glandular (1990)
stomach
Table 17. (contd).
Species
Route of Number of Dosage Time of Result Remarks Reference
exposure animals treatment
Rat
oral 7-10 m per 100 mg/kg 7 weeks increased number of liver foci relatively weak Stenius et al.
group diet per dayd decreased number of liver
foci inducer of enzyme- (1989)
200
mg/kg compared to
the 100 mg/kg altered liver foci
diet
per dayd
dose
Hamster
oral 15 m 0.5% in basal 20 weeks no proliferative changes in Hirose et al.
diet
forestomach (1986)
a after initiating dose of benzo[ a]
pyrene (BP)
b after initiating with N-butyl-2 N-(4-hydroxybutyl)
nitrosamine for four weeks
c one week after 150 mg/kg body weight
d after partial hepatectomy
In male mice centrilobular fatty
changes and cytomegaly were
found in the animals killed at 15 months,
but these findings were
not seen in mice killed at 2 years. The
authors reported that
hydroquinone dosing stopped two weeks
before necropsy and that the
microscopic lesions were likely to be
reversible after cessation of
treatment. There was a significantly
(P=0.0005) increased incidence
of hepatocellular adenomas in female mice
given hydroquinone for 2
years (controls 2/55, low dose 15/55, high
dose 12/55) and the
incidences of hepatocellular carcinomas were
1/55, 2/55 and 2/55,
respectively. In males the incidence of
adenomas was increased in
treated mice but the incidence of
hepatocellular carcinomas was
decreased. Preneoplastic changes
(anisokaryosis, multinucleated
hepatocytes, and basophilic foci) were
increased in high-dose male
mice. Treatment-related, but not
statistically significant,
follicular cell hyperplasia of the thyroid
gland was observed in
both male and female mice (NTP, 1989; Kari et al., 1992).
The NTP concluded that there was
"some evidence of carcinogenic
activity" of hydroquinone for male
F-344/N rats (tubular cell
adenomas of the kidney) and also for female
F-344/N rats
(mononuclear cell leukaemia). There was
"no evidence of carcinogenic
activity" for male B6C3F1
mice and "some evidence of carcinogenic
activity" for female B6C3F1
mice (hepatocellular adenomas and
carcinomas combined).
Shibata et al. (1991) administered hydroquinone at
dietary
levels of 0.% or 8 g/kg to groups of 30
Fischer-344 rats and
B6C3F1 mice of each sex. The
rats were dosed for 104 weeks and the
mice for 96 weeks. Average daily intakes
were reported to be 351 and
368 mg/kg body weight per day in male and
female rats, respectively,
and 1046 and 1486 mg/kg per day in male and
female mice,
respectively. No treatment-related clinical
signs and no significant
differences in mortality were found between
treated and control
animals of either species. The final body
weight was significantly
(P < 0.05) lower in treated female rats
than in corresponding
controls. In male rats the absolute and
relative liver and kidney
weights were significantly (P < 0.01)
increased, but in females
this applied only to the relative kidney
weights (P < 0.05).
Histologically, chronic nephropathy was
seen in both control and
treated groups of male rats. However,
treated males were more
severely affected than the controls, while
treated females showed
only slight nephropathy. The incidence of
epithelial hyperplasia of
the renal papilla was significantly (P <
0.05) increased in treated
male rats as was the incidence of renal
tubular hyperplasia (30/30)
and renal tubular adenomas (14/30).
The authors found that renal cell
tumour development in male
rats under the long-term influence of
hydroquinone was not
associated with alpha2u-globulin
nephropathy. The incidence of liver
foci showed a tendency to decrease in
treated males. A quantitative
analysis showed a statistically significant
(P < 0.05 in males, P<
0.01 in females) reduction in both sexes
given hydroquinone. The
authors did not find an increased incidence
of mononuclear cell
leukaemia in female rats (personal communication).
In mice, the final body weight was
significantly (P < 0.05)
lower in females given hydroquinone; the
relative liver and kidney
weights were significantly (P < 0.05)
increased. Histologically,
the incidence of squamous cell hyperplasia
of the forestomach
epithelium was significantly (P < 0.01)
increased in both sexes. A
significant increase in the incidence of
renal tubular hyperplasia
(P < 0.01) and three renal cell adenomas
were seen in 30 males
given hydroquinone. In treated males the
incidence of liver foci and
hepatocellular adenomas (14/30) was also
significantly (P < 0.05)
increased.
7.7.2
Carcinogenicity-related studies
7.7.2.1
Skin
In a study by Roe & Salaman
(1955), stock albino mice (24
males, "S" strain) were given a
single skin application of 0.3 ml of
a 6.7% solution of hydroquinone in acetone
(total dose 20.0 mg).
Three weeks later the mice received 18
weekly applications of 0.3 ml
of 0.5% croton oil in acetone as a promoter
on the same area of the
skin. Of the 24 treated animals, two died
during the experiment and
one mouse developed a skin papilloma.
In a two-stage carcinogenesis test on
mouse skin using
benzo[ a]pyrene (BP) as the
initiating agent, no tumour-promoting
activity was shown (Van Duuren &
Goldschmidt, 1976). Hydroquinone (5
mg) was applied to mouse skin (50 female
ICR/Ha Swiss mice/group;
both positive and negative controls) three
times weekly for 368
days, together with 5 µg BP. Hydroquinone
showed no potential as a
co-carcinogen when applied simultaneously
with BP; in fact, it
partially inhibited BP carcinogenicity.
7.7.2.2
Bladder
Implantation of cholesterol pellets
containing hydroquinone
into the urinary bladder of mice (strain
and sex unspecified) has
been studied by Boyland et al. (1964). The amount of hydroquinone
was 20% in 10 mg cholesterol pellets (2 mg
hydroquinone per mouse).
Bladder carcinomas were produced in 6 out
of 19 mice (32%) surviving
25 weeks. The incidence of urinary bladder
carcinomas in survivors
of the dosed group was significantly
(P=0.03) higher than in
controls (11.7%) given cholesterol pellets
only. However, the number
of animals surviving the study was low, and
the original number of
animals and their sex distribution were not
specified.
In a study by Kurata et al. (1990), groups of 20 male
Fischer-344 rats received 0.05% N-butyl- N-(4-hydroxybutyl)
nitrosamine in the drinking-water for four
weeks (as initiation)
followed by 8 g hydroquinone/kg in the
basal diet for 32 weeks. No
increase in the incidence of preneoplastic
lesions or
papillomas/carcinomas of the urinary
bladder was observed when
compared to the incidences in rats given
nitrosamine alone.
7.7.2.3
Stomach
Hirose et al. (1989) examined the promotion
activity and the
carcinogenic potential of some
dihydroxybenzenes, such as
hydroquinone, in the glandular stomach and
forestomach of F-344
rats. Groups of 15-16 male rats were given
a single intragastric
dose of 150 mg/kg body weight N-methyl- N'-nitro- N-
nitrosoguanidine (MNNG), followed one week
later by powdered diet
containing hydroquinone (8g/kg) or basal
diet alone for 51 weeks.
Further groups of 10 and 15 animals,
respectively, were administered
the basal diet alone or a diet containing
hydroquinone (8 g/kg) for
51 weeks without pretreatment with MNNG.
Hydroquinone did not cause
an increased incidence of forestomach or
glandular stomach lesions,
either with or without pretreatment with
MNNG, in comparison with
the control groups.
In studies performed by Hirose et al. (1986), hydroquinone
did
not produce proliferative lesions in the stomach of hamsters.
Male Syrian golden hamsters (15/group,
seven weeks old at the
beginning of the study) were given basal
diet with hydroquinone (5
g/kg) added or basal diet alone for 20
weeks. The dose was chosen as
approximately a quarter of the LD50.
Tissues from forestomach and
glandular stomach showed mild to moderate
hyperplasia in the group
given hydroquinone, but at the same
incidence as in the controls.
Similar results were obtained by Shibata et al. (1990) in an
8-week oral study using five male F-344
rats. Hydroquinone did not
induce any proliferative changes in the
forestomach or the glandular
stomach epithelium.
7.7.2.4
Liver
Hydroquinone has been shown to be a
relatively weak inducer of
enzyme-altered foci in rat liver when
tested for tumour-promoting
activity in a liver focus test (Stenius et al., 1989). Male
Sprague-Dawley rats (7-10/group) given
diethylnitrosamine (30 mg/kg
intraperitoneally) after partial
hepatectomy were treated with
hydroquinone (0, 100 and 200 mg/kg per day)
in their diet for 7
weeks. At 100 mg/kg there was a
significantly (P < 0.01) increased
number of liver foci and an increased focus
volume. The 200-mg dose
caused less foci (0.34 ± 0.16 per cm2)
than the 100-mg dose (0.65
± 0.25 per cm2), but the
incidence was higher than in the control
group (0.08 ± 0.08 per cm2).
A study by Kurata et al. (1990) yielded similar results
concerning the tumour-promoting potential
of hydroquinone in rats.
Dietary administration of hydroquinone
(8g/kg in basal diet) for 32
weeks, after initiation for four weeks with
N-butyl- N-
(4-hydroxybutyl) nitrosamine, caused no preneoplastic
lesions or
papillomas of the urinary bladder.
7.8.1 Effects on spleen and bone marrow cells;
immunotoxicity
The bone marrow is the target in
benzene toxicity; among the
many metabolites of benzene, hydroquinone
has received increased
scrutiny as one of the possible
contributing factors. Intravenous or
intraperitoneal administration of
hydroquinone (100 mg/kg) for three
consecutive days to male C57BL/6 CRIBR mice
significantly (P <
0.05) reduced the spleen and bone
marrow cellularity, with bone
marrow demonstrating the greatest
sensitivity (Wierda & Irons,
1982). Laskin et al. (1989) found that after injection
in Balb/c
mice hydroquinone (50 mg/kg) caused a
30-40% decrease in bone marrow
cellularity.
In vitro studies have demonstrated direct
myelotoxic effects
of hydroquinone toward mouse bone marrow
stromal cells (Gaido &
Wierda, 1984; Gaido & Wierda 1987).
Hydroquinone inhibited stromal
cell colony growth along with the ability
of these cells to support
granulocyte/monocyte colony formation in
co-culture. The bone marrow
stroma predominantly consists of
macrophages and fibroblastoid
stromal cells which interact to regulate
myelopoiesis. Treatment
with hydroquinone thus results in reduced
capacity of the stroma to
support myelopoiesis.
In addition to this cytotoxic effect,
Wierda & Irons (1982)
found in in vivo studies that hydroquinone also
affected the
immune function by reducing the number of
progenitor B-lymphocytes
in the spleen and bone marrow in mice, thus
demonstrating an
immunosuppressive potential. The rapid
generation and maturation of
progenitor B cells renders them highly
susceptible to toxic agents
that affect dividing cells. Evidence has
accumulated concerning the
effect of hydroquinone on the cellular
activity of the immune system
in vitro. Exposure of lymphocytes in vitro to hydroquinone has
been shown to result in a dose-dependent
inhibition of RNA synthesis
in the lymphocytes (Post et al., 1985). A hydroquinone
concentration of 1-2 x 10-5
mol/litre inhibited the RNA synthesis
by 50%.
In vitro exposure (one hour) of mouse bone
marrow cells to
hydroquinone (10-7-10-5
mol/litre) inhibited the maturation of
B-lymphocytes from pre B-cells after 24 and
48 h in culture (King
et al., 1987). More recent data have
demonstrated that
hydroquinone-induced inhibition of pre-B
cell maturation results
from toxicity to adherent stromal cells,
and that bone marrow
macrophages may be the primary target for
hydroquinone
myelotoxicity, rather than fibroblastic
stromal cells or pre-B cells
(King et al., 1989; Thomas et al., 1989a). Results also indicate
a dose-related reduction of macrophage
interleukin-1 (IL-1)
secretion in cultures of bone marrow
macrophages exposed to
hydroquinone (King et al., 1989; Thomas et al., 1989b). IL-1 is
necessary for the induction of
interleukin-4 (IL-4), which is
produced by fibroblastic stromal cells and
is required for
maturation of pre-B cells to B cells (King et al., 1989).
Fan et al. (1989) demonstrated that
hydroquinone can inhibit
the natural killer activity of mouse spleen
cells in vitro at low
concentrations. Concentrations of 1 x 10-5
mol/litre and 1 x
10-6 mol/litre inhibited 29 and
22% of the activity, respectively.
Lewis et al. (1988b) found that hydroquinone had
a selective
effect on macrophage functions important in
host defense. At
concentrations of 3-100 µmol/litre,
hydroquinone significantly
(P < 0.05) inhibited the release
of hydrogen peroxide and at 100
µmol/litre it significantly (P <
0.05) inhibited priming by
interferon for tumour cell cytolysis.
Cheung et al. (1989) have
shown a concentration-dependent inhibition
of interferon-alpha/ß
production following exposure to
hydroquinone in murine L-929 cell
cultures.
7.8.2
Effects on tumour cells
The cytotoxic activity of hydroquinone
has been tested on
different tumour cells. Chavin et al. (1980) studied the effect on
melanoma transplants in female BALB/c mice.
The incidence of
melanoma transplants was reduced and the
survival significantly (P
< 0.0005) increased in mice that
received hydroquinone treatment
(80 mg/kg).
Vladescu & Apetroae (1983) studied
the molecular mechanisms of
antitumour action and the possibilities of
using hydroquinone as a
toxic agent against cancer cells. In H 18R
tumour-bearing male
Wistar rats treated with hydroquinone (5
mg/kg per day) for seven
days, the catalase activity was markedly
depressed in liver, spleen,
blood and H 18R tumour. In vitro studies on tumour and liver
homogenates from normal and tumour-bearing
rats showed a marked
inhibition of catalase activity in the
tumour, which was less
evident in the liver. The activity was less
reduced in normal liver
homogenates. It was suggested that the
mechanism of action of
hydroquinone as an antitumour agent is
achieved mainly via peroxide
production.
When tested on cultured rat hepatoma
cells hydroquinone showed
a dose-dependent cytotoxic activity (Assaf et al. 1987). A dose of
33 mg/litre (300 µmol/litre) caused
cellular mortality of 40% after
24 h of incubation and 66 mg/litre (600
µmol/litre) resulted in 100%
cellular mortality.
Hydroquinone, given as single oral or
subcutaneous lethal
doses, causes nonspecific effects on the
nervous system such as
hyperexcitability, tremor and convulsions
in several experimental
animal species (see section 7.1). Animals
given sublethal oral doses
recover within a few days.
These central nervous system
stimulation effects were confirmed
in a 90-day oral study on rats (Eastman
Kodak Company, 1988) (see
also section 7.3). Male and female weanling
rats (CD(SD)BR),
initially seven weeks old, were treated
with hydroquinone (20, 64 or
200 mg/kg per day) dissolved in water at a
concentration of 5%.
Doses were given by gavage 5 days per week.
Functional-observational
battery examinations were performed
throughout the study. The
battery included observations of body
position, activity level,
coordination of movement and gait,
behaviour, presence of
convulsions, tremors, lacrimation,
salivation, piloerection,
pupillary dilatation or constriction,
respiration, diarrhoea,
urination, vocalization, forelimb/hindlimb
grip strength and sensory
function. Tremors and depression of general
activity were observed
in both sexes shortly after dosing with 64
or 200 mg
hydroquinone/kg. Functional-observational
battery examinations did
not result in any evidence of neurotoxicity
as assessed by
quantitative grip strength measurement,
brain weight or
neuropathological examination. The NOEL was
considered to be 20 mg
hydroquinone/kg body weight.
Otsuka & Nonomura (1963) reported
that hydroquinone reversed
curare blockage at neuromuscular junctions
in frog sciatic nerve -
sartorius muscle preparations. The authors
suggested that this
effect was due to an increased release of
transmitter at the
neuromuscular junction induced by
hydroquinone.
Until recently, exposure to
hydroquinone has not been
associated with nephrotoxicity.
Nephrotoxicity has not been reported
following either occupational exposure to hydroquinone
or acute
exposures in humans. Carlson & Brewer
(1953) gave human volunteers
daily hydroquinone doses of 300 or 500
mg/day for periods of up to
20 weeks without effects on urinalysis
parameters. Exposure of five
male mixed-breed dogs to 100 mg
hydroquinone/kg per day for 26 weeks
had no effect on urinalysis parameters or
renal histopathology
(Carlson & Brewer, 1953). Christian et al. (1976) reported that
exposure of Carworth rats to hydroquinone
in the drinking-water at
concentrations of up to 10 g/litre (6 rats
of each sex per group for
8 weeks) or up to 4 g/litre (20 rats of
each sex per group for 15
weeks) resulted in slight changes in kidney
weight but no
histopathological changes. Carlson &
Brewer (1953) also reported no
evidence of renal histopathological changes
in Sprague-Dawley rats
fed diets containing 10g hydroquinone/kg
for 104 weeks.
NTP (1989) reported that oral gavage
of hydroquinone (0, 25,
50, 100, 200 or 400 mg/kg) in corn oil for
13 weeks resulted in
toxic nephropathy in F-344 rats at the two
highest dose levels (200
mg/kg: 7/10 males, 6/10 females; 100 mg/kg:
1/10 females). Oral
gavage of 0, 25 or 50 mg/kg in water for 15
months resulted in an
increased incidence of chronic nephropathy
in male F-344 rats (25
mg/kg: 5/5 males; 50 mg/kg: 6/10 males).
When male F-344 rats were
dosed at 0, 25 or 50 mg/kg for two years,
there was an increased
severity of chronic progressive nephropathy
in 20/55 animals given
50 mg/kg. At a dosage level of 50 mg/kg for
either 15 months or 2
years, male rats had heavier relative
kidney weights.
Shibata et al. (1991) also reported that F-344
rats developed
chronic nephropathy when fed 8g hydroquinone/kg
diet for 2 years.
Male rats showed increased relative and
absolute kidney weight, as
well as an increased severity of chronic
nephropathy (14/30
animals). Female rats showed an increased
relative kidney weight,
but only a minimal increase in severity of
chronic nephropathy in
7/30 animals.
Boatman et al. (1992) reported on the urinalysis
changes
observed in male and female F-344 rats and
Sprague-Dawley rats given
single doses of 0, 200 or 400 mg hydroquinone/kg
in water by oral
gavage. B6C3F1 mice were
examined after receiving doses of 0 or
350 mg/kg in a similar fashion. The
placement of venous catheters in
F-344 rats increased their response to
hydroquinone. At 400 mg/kg,
male and female F-344 rats, but not
Sprague-Dawley rats, displayed
pronounced enzymuria and glucosuria, which
resolved in 72-96 h. At
200 mg/kg, enzymuria and glucosuria were
present in female F-344
rats but not males. Epithelial cell counts
in the urine were
statistically significantly increased (P <
0.05) at 400 mg/kg
(male and female F-344 rats only) and 200
mg/kg (female F-344 rats
only). Statistically significant (P <
0.05) decreases in
osmolality were reported at 400 mg/kg for
F-344 (both sexes) and
female Sprague-Dawley rats. Diuresis (ml
urine/h) was statistically
significant (P < 0.005) only for
female F-344 rats at 200 mg/kg
and 400 mg/kg. Although differences were
observed in some of the
urinary parameters measured, mice were
generally not responsive to
hydroquinone.
To characterize the early development
of renal toxicity in
rats, cell proliferation was quantified
within the proximal (P1, P2
and P3) and distal tubular segments of the
kidney in rats given 0,
2.5, 25 or 50 mg hydroquinone/kg by oral
gavage. Male and female
F-344 rats were treated for 1, 3 or 6
weeks, and male Sprague-Dawley
rats were treated for 6 weeks. At 6 weeks,
an 87% increase in cell
proliferation was measured in the P1
segment, a 50% increase in the
P2 segment, and a 34% increase in the P3
segment from kidneys of
male F-344 rats dosed with 50 mg/kg.
Urinalysis indicated increased
enzymuria in this same dose group, and mild
histological changes
were present in the kidneys. Animals
examined at other time points
or from other dose groups were not affected
by hydroquinone.
The increased incidence of renal
adenomas only in male F-344
rats (NTP, 1989) has led to speculation
that the tumours observed
may be related to alpha2u-globulin-induced
nephropathy. This
mechanism of action for induction of kidney
tumours does not appear
to be relevant for hydroquinone as none of
the studies cited above
has reported finding evidence of hyalin
droplet nephropathy
following subacute, subchronic or chronic
hydroquinone exposure.
Glutathione metabolites, which are at
least partially formed in
the liver and transported to the kidney,
are reported to be involved
in the nephrotoxicity observed. Some of the
potential glutathione
