Genetic Toxicology - Mammalian Cell Mutagenicity

Study Information
Study Attribute	Value
CEBS Accession Number:	002-02439-0007-0000-7
Chemical Name:	Methyl isocyanate
CASRN:	624-83-9
NTP Study Type:	Genetic Toxicology - Mammalian Cell Mutagenicity
NTP Study ID:	752783
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: Positive
		Conc. ug/mL	Cloning Efficiency	Relative Total Growth	Mutant Colonies	Mutant Frequency	Avg Mutant Frequency
Vehicle Control	Dimethyl Sulfoxide	0	99	116	98	33	34
			88	108	67	25
			80	100	82	34
			77	76	99	43
Test Chemical	Methyl isocyanate	0.5	61#	64	41	23	35
			67	58	88	44
			53	52	64	40
		0.75	42	44	51	40	43
			51	36	63	42
			55#	40	75	46
		1	55	33	89	54	49
			52	27	93	59
			63	58	65	34
		1.5	32	13	119	123	147*
			34#	14	176	172
			45	12	198	146
		2	35	18	104	100	130*
			43#	9	213	165
			38#	9	143	126
		3	36#	3	213	196	171*
			43	4	236	185
			53#	7	206	130
Positive Control	Methyl Methane Sulfonate	5	39#	21	519	442	454*
Positive Control			40#	12	552	466	454*

Nonactivation Trial: 2 Experiment Call: Positive
		Conc. ug/mL	Cloning Efficiency	Relative Total Growth	Mutant Colonies	Mutant Frequency	Avg Mutant Frequency
Vehicle Control	Dimethyl Sulfoxide	0	103	92	41	13	21
			105#	108	87	28
			99	100	71	24
			96	99	50	17
Test Chemical	Methyl isocyanate	0.5	46	45	49	36	48*
			51	39	101	67
			45	40	56	42
		0.75	80	60	36	15	56*
			20	17	48	81
			46	37	100	72
		1	34	25	111	110	74*
			42	29	115	92
			58	43	34	19
		1.5	50	17	164	109	130*
			49	12	217	147
			37	16	148	135
		2	66	12	366	185	169*
			32	7	186	195
			54	13	204	126
		3	38	2	246	216	281*
			39	3	364	310
			48	5	452	317
Positive Control	Methyl Methane Sulfonate	5	65	40	547	283	254*
			63	35	502	266
			66#	47	422	213

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