Genetic Toxicology - Mammalian Cell Mutagenicity

Study Information
Study Attribute	Value
CEBS Accession Number:	002-02062-0011-0000-4
Chemical Name:	Dimethyl hydrogen phosphite
CASRN:	868-85-9
NTP Study Type:	Genetic Toxicology - Mammalian Cell Mutagenicity
NTP Study ID:	199344
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: 1 Experiment Call: Inconclusive
		Conc. ug/mL	Cloning Efficiency	Relative Total Growth	Mutant Colonies	Mutant Frequency	Avg Mutant Frequency
Vehicle Control	Fischer Medium	0	85	110	77	30	30
			84	104	77	30
			81#	86	68	28
			143r	155	74	17
Test Chemical	Dimethyl hydrogen phosphite	125	75	111	78	35	37
			91	109	107	39	37
		250	102	122	78	25	23
			92	114	58	21	23
		500	60	91	49	27	22
			113	124	53	16	22
		1000	99#	84	97	33	31
			83	79	73	29	31
		2000	88	68	108	41	40
			93	62	110	40	40
Positive Control	Methyl Methane Sulfonate	15	41	34	238	193	197*
Positive Control			54	37	323	200	197*

Nonactivation Trial: 2 Experiment Call: Negative
		Conc. ug/mL	Cloning Efficiency	Relative Total Growth	Mutant Colonies	Mutant Frequency	Avg Mutant Frequency
Vehicle Control	Fischer Medium	0	112	106	226	67	73
			90	98	180	67
			93	105	205	73
			74	91	184	83
Test Chemical	Dimethyl hydrogen phosphite	600	88	79	172	65	72
			78	84	184	79	72
		1000	90	85	147	55	65
			70	71	160	76	65
		1400	76	75	203	90	86
			83	70	202	82	86
		1800	58	39	174	101	88
			79	57	176	75	88
		2200	70	20	233	111	107
			95	28	295	104	107
		2600

Positive Control	Methyl Methane Sulfonate	15	29	19	356	414	444*
Positive Control			20	18	289	474	444*

Induced S9 Trial: 1 Experiment Call: Positive
		Conc. ug/mL	Cloning Efficiency	Relative Total Growth	Mutant Colonies	Mutant Frequency	Avg Mutant Frequency
Vehicle Control	Fischer Medium	0	43r	104	69	54	42
			69	103	96	46
			45r	82	54	40
			51	97	57	38
Test Chemical	Dimethyl hydrogen phosphite	1700	50	74	101	68	70*
			36	62	77	72	70*
		1900	40	56	54	45	49
			34	54	54	52	49
		2100	26	48	75	97	106*
			28	41	97	115	106*
		2300	11	14	61	194
			3r	4	18	225
		2500	7r	8	23	118
			1r	1	9	450
Positive Control	3-Methylcholanthrene	2.5	49	50	463	314	373*
Positive Control			32	33	419	432	373*

Induced S9 Trial: 2 Experiment Call: Positive
		Conc. ug/mL	Cloning Efficiency	Relative Total Growth	Mutant Colonies	Mutant Frequency	Avg Mutant Frequency
Vehicle Control	Fischer Medium	0	92	99	110	40	39
			88	101	100	38
			121r	111	139	38
			130r	106	133	34
Test Chemical	Dimethyl hydrogen phosphite	1700	148r	95	227	51
			124r	74	222	60
		1900	103	76	189	61	62
			100	74	188	62	62
		2100	100	72	235	78	79*
			101	77	245	81	79*
		2300	112	69	243	72	71*
			103	68	217	70	71*
		2500	89	48	378	141
			134r	44	509	126
Positive Control	3-Methylcholanthrene	2.5	92	40	775	282	288*
Positive Control			84	44	736	293	288*

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