Hydroquinone

Genetic toxicity: in vitro

Administrative data

Endpoint:

in vitro gene mutation study in mammalian cells

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

comparable to guideline study

Data source

Reference

Reference 1

Reference Type:

publication

Title:

Responses of the L1578Y tk+/tk- mouse lymphoma cell forward mutation assay. II. 18 coded chemicals.

Author:

McGregor DB, Brown A, Cattanach P, Edwards I, McBride D, Caspary WJ

Year:

1988

Bibliographic source:

Environ Molec Mutagen 11, 91 - 118

Reference 2

Reference Type:

study report

Title:

Unnamed

Year:

1989

Report date:

1989

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 476 (In Vitro Mammalian Cell Gene Mutation Test)

GLP compliance:

no

Type of assay:

mammalian cell gene mutation assay

Test material

Test material information

Constituent 1

Reference substance name:

Hydroquinone

EC Number:

204-617-8

EC Name:

Hydroquinone

Cas Number:

123-31-9

Molecular formula:

C6H6O2

IUPAC Name:

hydroquinone

Details on test material:

- Name of test material (as cited in study report): hydroquinone

Method

Target gene:

Thymidine kinase locus

Species / strain

Species / strain / cell type:

mouse lymphoma L5178Y cells

Details on mammalian cell type (if applicable):

- Type and identity of media: Fischer's medium with 5% heat-inactivated horse serum
- Properly maintained: yes
- Periodically checked for Mycoplasma contamination: yes
- Periodically "cleansed" against high spontaneous background: yes

Metabolic activation:

with and without

Metabolic activation system:

S9 mix from Aroclor 1254 induced rat liver

Test concentrations with justification for top dose:

- S9: 1.56, 3.12, 6.25, 12.5, 25, 50 µg/mL
+ S9: 0.652, 1.25, 2.5, 5, 10 µg/mL

Vehicle / solvent:

- Vehicle(s)/solvent(s) used: DMSO (+ S9), methanol (- S9)

Controls

Untreated negative controls:

yes

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

other: - S9: EMS; + S9: EMS or 3-methylcholanthrene

Details on test system and experimental conditions:

METHOD OF APPLICATION: in medium

DURATION
- Exposure duration: 4 h
- Expression time (cells in growth medium): 2 d
- Selection time (if incubation with a selection agent): 11-14 d
- Fixation time (start of exposure up to fixation or harvest of cells): 13-16 d

SELECTION AGENT (mutation assays): trifluorothymidine

NUMBER OF REPLICATIONS: 2, two independent assays

DETERMINATION OF CYTOTOXICITY
- Method: relative total growth

Evaluation criteria:

Positive response: dose-related trend and statistically significant response at one of the three highest doses

Statistics:

Dose trend test (Barlow et al., 1972); variance analysis (pairwise comparisons) with P < 0.05

Results and discussion

Test results

Species / strain:

mouse lymphoma L5178Y cells

Metabolic activation:

with and without

Genotoxicity:

positive

Cytotoxicity / choice of top concentrations:

cytotoxicity

Vehicle controls validity:

valid

Positive controls validity:

valid

Any other information on results incl. tables

Table: Results of the mouse lymphoma cell mutation assay without and with metabolic activation

Metabolic activation / trial	Test concentration	Cloning efficiency (%)	Relative total growth (%)	Mutant fraction	Average mutant fraction
- S9 / trial 1	0	47	68	73	74
		35	57	96
		48	164	62
		60	110	65
	1.562	41	45	200	157*
		42	108	113
	3.125	25	23	454	333*
		42	50	213
	6.25	17	7	857	624*
		25	13	391
	12.5	TOX
		TOX
	Positive control	47	101	214	197*
		45	43	181
- S9 / trial 2	0	76	96	19	22
		61	100	28
		93	98	18
		85	106	24
	3.125	13	5	565	419*
		57	30	274
	6.25	48	13	542	542*
		37	9	541
	12.5	27	7	871	857*
		25	7	843
	25	28	6	863	774*
		30	7	685
	50	TOX
		TOX
	Positive control	120	114	108	108
- S9 / trial 3	0	93	114	19	38
		62	109	47
		52	90	42
		90	87	45
	0.625	81	68	47	49
		102	71	51
	1.25	36	22	164	179*
		27	16	195
	2.5	15	7	607	624*
		12	4	642
	5	TOX
		12	1	1915
	10	TOX
		TOX
	Positive control	69	66	299	306*
		93	58	313
+ S9 / trial 1	0	91	99	65	70
		70	102	67
		68	98	70
		79	100	77
	0.625	93	116	67	72
		90	133	78
	1.25	81	105	69	78
		72	99	86
	2.5	75	81	138	134*
		98	93	130
	5	61	20	338	328*
		70	18	318
	10	43	7	485	464*
		44	7	582
	Positive control	55	57	423	451*
		45	47	480

* Statistically significant increase compared to vehicle controls, P < 0.05

Applicant's summary and conclusion

Conclusions:

Positive with and without metabolic activation.

In the mouse lymphoma assay for induction of trifluorothymidine resistance in L5178Y/TK cells, HQ was positive at doses of 1.25 µg/mL and higher in the absence of S9, and at 2.5 µg/mL and higher in the presence of S9.

Executive summary:

Hydroquinone was tested in a mouse lymphoma mutation assay for induction of trifluorothymidine resistance in L5178Y/TK cells with a test protocol similar to OECD Guideline 476. Test concentrations of HQ ranged from 0.625-50 µg/mL without S9 mix and 0.625-10 µg/mL with S9 mix. Treatment time was 4 h, followed by a 2-day expression period and a 11 to 14-day selection period in the presence of TFT. Cytotoxicity was indicated by relative total growth. The lowest effective dose with a significantly increased mutant fraction was 1.25 µg/mL without S9 (relative total growth 32%), and 2.5 µg/mL with S9 (relative total growth 87%). The mutant fraction was statistically significantly and dose-dependantly increased from these concentrations up. HQ was positive in the mouse lymphoma assay both in the presence and absence of S9.