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Study Information
Study Attribute Value
CEBS Accession Number: 002-02419-0013-0000-2
Chemical Name: Methoxychlor
CASRN: 72-43-5
NTP Study Type: Genetic Toxicology - Mammalian Cell Mutagenicity
NTP Study ID: G16413
Study Result: Positive


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: No Call
  Conc.
ug/mL 		Cloning
Efficiency 		Relative Total
Growth 		Mutant Colonies Mutant Frequency Avg Mutant Frequency
Vehicle Control Dimethyl Sulfoxide 
 0         
 130r 84 98 25
    147r 141 84 19
Test Chemical Methoxychlor 
50         
 104 47 79 25 28
    86 44 78 30
  
75         
 92 39 92 33 29
    106 55 79 25
  
100         
 130r 31 125 32
    98r 47 84 28
  
150         
 109 17 96 29 30
    104 22 98 31
  
200         
 99 9 79 27 25
    82 9 59 24
Positive Control Ethyl Methane Sulfonate 
500         
 80 33 831 346 384*
    76 25 957 422
Negative Control Negative (Not Specified) 
 0         
 117 99 100 29 31*
    120 101 117 33

Nonactivation Trial: 2 Experiment Call: No Call
  Conc.
ug/mL 		Cloning
Efficiency 		Relative Total
Growth 		Mutant Colonies Mutant Frequency Avg Mutant Frequency
Vehicle Control Dimethyl Sulfoxide 
 0         
 82 117 96 39 40
    68 67 84 41
Test Chemical Methoxychlor 
100         
 177r 46 352 66
    32r 11 108 112
  
150         
 73r 9 161 73
  
200         
 105# 10 200 63 64
    71 8 139 65
  
225         
 78 5 166 71 54
    82# 6 91.5 37
  
250         
 67 5 119 59 58
    69 5 115 56
Positive Control Ethyl Methane Sulfonate 
500         
 49 42 862 590 587*
    51 38 886 583
Negative Control Negative (Not Specified) 
 0         
 87 115 79 30
    48r 54 85 59

Nonactivation Trial: 3 Experiment Call: Negative and Non-Toxic
  Conc.
ug/mL 		Cloning
Efficiency 		Relative Total
Growth 		Mutant Colonies Mutant Frequency Avg Mutant Frequency
Vehicle Control Dimethyl Sulfoxide 
 0         
 52 89 57 37 29
    85 121 67 26
    60 101 45 25
    62 89 53 28
Test Chemical Methoxychlor 
12.5       
 57 123 39 23 22
    61 103 42 23
    103 149 64 21
  
25         
 74 80 37 17 29
    55 93 73 45
    67 90 52 26
  
50         
 49 51 61 42 40
    46 50 45 33
    44 48 60 46
  
75         
 49 36 45 31 35
    65 24 66 34
    55 35 66 40
  
100         
 48 17 85 59 41
    58 20 66 38
    52 22 43 28
  
150         
 75 12 121 54 60*
    52 12 111 70
    68 14 111 54
Positive Control Ethyl Methane Sulfonate 
500         
 26 13 582 737 882*
    13 12 422 1096
    16 14 398 812

Nonactivation Trial: 4 Experiment Call: Negative and Non-Toxic
  Conc.
ug/mL 		Cloning
Efficiency 		Relative Total
Growth 		Mutant Colonies Mutant Frequency Avg Mutant Frequency
Vehicle Control Dimethyl Sulfoxide 
 0         
 67 119 46 23 24
    53 100 54 34
    59 88 38 22
    76 93 37 16
Test Chemical Methoxychlor 
12.5       
 104 107 52 17 23
    89 78 67 25
    74 84 58 26
  
25         
 94 70 61 22 26
    75 68 53 23
    72 70 69 32
  
50         
 92 53 43 16 23
    56 36 56 33
    88 54 55 21
  
75         
 70 25 57 27 24
    101 38 49 16
    66 25 54 27
  
100         
 60 5 77 43 47*
    71 6 98 46
    71 7 113 53
  
150         
   
   
Positive Control Ethyl Methane Sulfonate 
500         
 35 43 589 558 461*
    42 57 488 386
    40 47 521 438

Non-Induced S9 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         
 100 96 106 35 38
    85 86 106 42
Test Chemical Methoxychlor 
12.5       
 77 56 105 45 52
    72 31 127 59
  
25         
 71 21 238 111 106*
    65 26 197 101
  
50         
 67 25 208 103 123*
    64 13 276 143
  
75         
 47 9 191 136 144*
    51 9 234 152
  
100         
    86 8 148 57
  
125         
   
Positive Control 3-Methylcholanthrene 
7         
 85 39 383 150 150*
    123r 78 347 94
Negative Control Negative (Not Specified) 
 0         
 101 148 75 25 30*
    92 70 96 35

Induced S9 Trial: 1 Experiment Call: Negative and Non-Toxic
  Conc.
ug/mL 		Cloning
Efficiency 		Relative Total
Growth 		Mutant Colonies Mutant Frequency Avg Mutant Frequency
Vehicle Control Dimethyl Sulfoxide 
 0         
 92 106 105 38 49
    73 99 131 60
Test Chemical Methoxychlor 
12.5       
 62 16 231 124 138*
    58 15 262 151
  
25         
 54 15 220 137 195*
    42 7 320 254
  
50         
 54 11 243 149 160*
    51 9 262 171
  
75         
   
Positive Control 3-Methylcholanthrene 
5         
 34 8 356 352 402*
    34 14 461 452
Negative Control Negative (Not Specified) 
 0         
 76 90 118 52 50*
    90 106 128 47

Induced S9 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         
 74 122 75 34 36
    72 80 81 38
Test Chemical Methoxychlor 
5         
 61 36 127 69 59
    72 41 104 48
  
10         
 58 43 155 90 80*
    57 27 118 69
  
20         
 50 18 152 101 99*
    50 20 144 97
  
40         
 45 17 131 98 91*
    56 17 142 85
  
80         
 54 21 151 94 89*
    43 19 107 84
Positive Control 3-Methylcholanthrene 
5         
 27 14 230 284 257*
    39 20 269 230
Negative Control Negative (Not Specified) 
 0         
 79 110 67 28 30*
    71 87 69 32

Induced S9 Trial: 3 Experiment Call: Positive
  Conc.
ug/mL 		Cloning
Efficiency 		Relative Total
Growth 		Mutant Colonies Mutant Frequency Avg Mutant Frequency
Vehicle Control Dimethyl Sulfoxide 
 0         
 82 114 141 58 49
    77 83 139 60
    73 115 85 39
    89 89 105 39
Test Chemical Methoxychlor 
5         
 47 55 82 59 59
    60 70 107 59
  
10         
 64 53 137 71 76
    57 33 137 80
  
20         
 77 26 201 88 97*
    53 27 171 107
  
40         
 71 30 184 86 78*
    71 39 150 70
  
60         
 61 28 168 92 90*
    80 37 208 87
  
80         
 57 25 186 109 92*
    74 36 167 75
Positive Control 3-Methylcholanthrene 
5         
 41 27 468 384 379*
    35 27 434 417
    47 33 469 335

Induced S9 Trial: 4 Experiment Call: Positive
  Conc.
ug/mL 		Cloning
Efficiency 		Relative Total
Growth 		Mutant Colonies Mutant Frequency Avg Mutant Frequency
Vehicle Control Dimethyl Sulfoxide 
 0         
 89 94 145 54 53
    91 104 121 44
    103 94 174 56
    82 108 135 55
Test Chemical Methoxychlor 
5         
 82 67 146 59 63
    95 51 169 59
    89# 65 185 69
  
10         
 80 25 213 88 92*
    91 31 225 83
    75 19 237 106
  
20         
 102 18 282 92 93*
    78 16 229 98
    75 20 201 90
  
40         
 99# 18 271 91 95*
    81 21 253 105
    81 18 220 91
  
60         
 110 23 251 76 78*
    85 20 215 84
    82 18 183 75
  
80         
 74 22 215 97 93*
    92 19 254 92
    82 13 218 89
  
100         
   
   
Positive Control 3-Methylcholanthrene 
2.5       
 58 35 451 258 274*
    68# 35 593 291
    67 42 551 275

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