Genetic Toxicology - Mammalian Cell Mutagenicity

Study Information
Study Attribute	Value
CEBS Accession Number:	002-02269-0010-0000-2
Chemical Name:	Hydroquinone
CASRN:	123-31-9
NTP Study Type:	Genetic Toxicology - Mammalian Cell Mutagenicity
NTP Study ID:	327913
Study Result:	Positive

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Table Instructions and Notes:
Studies are indicated to be "Nontoxic" when the observed reductions in relative total growth did not indicate that the maximum tolerated dose was achieved.

Nonactivation Trial: 2 Experiment Call: Positive
		Conc. ug/mL	Cloning Efficiency	Relative Total Growth	Mutant Colonies	Mutant Frequency	Avg Mutant Frequency
Vehicle Control	Methanol	0	85#	106	60	24	22
			93	98	49	18
			61	100	51	28
			76	96	43	19
Test Chemical	Hydroquinone	3.125	13	5	226	565	419*
			58	30	472	274	419*
		6.25	37	9	598	541	542*
			48	13	778	542	542*
		12.5	25	7	624	843	857*
			27	7	697	871	857*
		25	30#	7	610.5	686	773*
			28#	6	716	860	773*
		50

Positive Control	Ethyl Methane Sulfonate	250	120#	114	390	108	108*

Nonactivation Trial: 3 Experiment Call:
		Conc. ug/mL	Cloning Efficiency	Relative Total Growth	Mutant Colonies	Mutant Frequency	Avg Mutant Frequency
Vehicle Control	Dimethyl Sulfoxide	0	90	87	123	45	38
			52	90	65	42
			62	109	88	47
			93	114	54	19
Test Chemical	Hydroquinone	0.625	102	71	156	51	49
			81	68	115	47	49
		1.25	28	16	161	195	179*
			36	22	175	164	179*
		2.5	12	4	231	642	624*
			15	7	270	607	624*
		5	13	1	718	1915

		10

Positive Control	Ethyl Methane Sulfonate	250	93	58	873	313	306*
Positive Control			70	66	623	299	306*

Induced S9 Trial: 2 Experiment Call:
		Conc. ug/mL	Cloning Efficiency	Relative Total Growth	Mutant Colonies	Mutant Frequency	Avg Mutant Frequency
Vehicle Control	Dimethyl Sulfoxide	0	79	100	183	77	70
			68	98	144	70
			70	102	142	67
			91	99	176	65
Test Chemical	Hydroquinone	0.625	94	116	187	67	72
			90	133	210	78	72
		1.25	81	105	169	69	78
			73	99	188	86	78
		2.5	98	93	380	130	134*
			75	81	310	138	134*
		5	61	20	619	338	328*
			70	18	670	318	328*
		10	44	7	582	443	464*
			43	7	630	485	464*
Positive Control	3-Methylcholanthrene	2.5	45	47	653	480	451*
Positive Control			55	57	693	423	451*

Footnotes:
Asterisks(*) indicate significant responses.
r = rejected value due to quality control criteria
# = reduced sample size because of the loss of one culture dish due to contamination