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Study Information
Study Attribute Value
CEBS Accession Number: 002-01341-0011-0000-3
Chemical Name: 2-Mercaptobenzimidazole
CASRN: 583-39-1
NTP Study Type: Genetic Toxicology - Mammalian Cell Mutagenicity
NTP Study ID: 751815
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: Inconclusive
  Conc.
ug/mL 		Cloning
Efficiency 		Relative Total
Growth 		Mutant Colonies Mutant Frequency Avg Mutant Frequency
Vehicle Control Dimethyl Sulfoxide 
 0         
 82 94 52 21 28
    85 106 75 30
    78 108 82 35
    83 92 63 25
Test Chemical 2-Mercaptobenzimidazole 
12.5       
 63 70 60 32 26
    80 84 58 24
    92 106 62 22
  
25         
 69 84 80 39 33
    79 89 71 30
    99 111 92 31
  
50         
 68 67 83 41 36
    92 88 99 36
    72 71 69 32
  
75         
 62 64 72 39 34
    85 74 84 33
    79 74 75 32
  
100         
 82 55 67 27 28
    73 60 78 36
    77 67 48 21
  
150         
 90 40 63 23 33
    73 37 89 41
    75 45 82 36
Positive Control Methyl Methane Sulfonate 
5         
 47 28 341 244 262*
    51 40 380 248
    56 42 492 293

Nonactivation Trial: 2 Experiment Call: Inconclusive
  Conc.
ug/mL 		Cloning
Efficiency 		Relative Total
Growth 		Mutant Colonies Mutant Frequency Avg Mutant Frequency
Vehicle Control Dimethyl Sulfoxide 
 0         
 83# 90 94 38 32
    89 97 84 31
    101 95 98 32
    93 118 70 25
Test Chemical 2-Mercaptobenzimidazole 
12.5       
 94 72 112 40 38
    117 92 115 33
    90 74 111 41
  
25         
 97 74 116 40 32
    114 86 103 30
    113 79 86 25
  
50         
 83 56 100 40 36
    90 59 102 38
    95 75 85 30
  
75         
 92# 67 62 22 32
    106 58 99 31
    95 63 122 43
  
100         
 127r 72 112 29 29
    111 64 91 27
    105 62 97 31
  
150         
 95 38 90 31 37
    103 45 138 45
    102 46 107 35
Positive Control Methyl Methane Sulfonate 
5         
 104# 78 941 300 328*
    65 44 825 423
    74 41 574 260

Nonactivation 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         
 98 105 125 43 41
    86# 89 122 47
    91 97 114 42
    99 109 95 32
Test Chemical 2-Mercaptobenzimidazole 
12.5       
 98 98 106 36 38
    98 113 115 39
    90 86 107 40
  
25         
 96 84 120 42 40
    107 85 111 35
    101 67 130 43
  
50         
 128r 81 127 33 41
    84 72 99 39
    83 74 107 43
  
100         
 91 65 113 42 45
    81 68 112 46
    95 65 136 48
  
200         
 97 55 161 55 57
    73 41 128 59
    73 45 124 57
  
300         
 58 19 147 85 70*
    92 28 163 59
    54 27 106 65
  
500         
   
   
Positive Control Methyl Methane Sulfonate 
5         
 59 34 502 284 265*
    56 41 421 250
    57 36 449 262

Nonactivation 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         
 108 117 75 23 30
    110 53 94 29
    99 106 110 37
    113# 124 110 32
Test Chemical 2-Mercaptobenzimidazole 
25         
 105 80 84 27 25
    126r 102 67 18
    92 81 66 24
  
50         
 104 66 116 37 33
    124r 67 115 31
    112 56 96 29
  
100         
 117 59 273 78 58*
    121r 55 117 32
    120 54 139 39
  
200         
 128r 30 231 60
    110 35 273 83
    129r 31 298 77
  
300         
 106 23 277 87 106*
    101 14 363 120
    89 13 300 112
  
400         
   
  
500         
   
   
Positive Control Methyl Methane Sulfonate 
5         
 67 48 589 294 357*
    56# 37 658 392
    69 43 795 384

Nonactivation Trial: 5 Experiment Call: Positive
  Conc.
ug/mL 		Cloning
Efficiency 		Relative Total
Growth 		Mutant Colonies Mutant Frequency Avg Mutant Frequency
Vehicle Control Dimethyl Sulfoxide 
 0         
 71 89 129 61 43
    77 91 75 33
    77 109 92 40
    64 111 75 39
Test Chemical 2-Mercaptobenzimidazole 
25         
 67 78 74 37 42
    61 61 90 49
    91 63 106 39
  
50         
 111 41 123 37 34
    110 54 97 29
    76 39 81 36
  
100         
 86 16 263 102 111*
    77 16 339 146
    90 15 229 85
  
150         
 67 5 149 74 64
   
    99 11 158 53
  
200         
   
   
Positive Control Methyl Methane Sulfonate 
5         
 69 50 567 273 232*
    73 57 510 234
    52 50 293 187

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         
 68 95 122 60 61
    83 112 145 58
    75 104 110 49
    67 90 153 76
Test Chemical 2-Mercaptobenzimidazole 
 0.156     
 53 37 114 72 74
    48 43 99 68
    52 39 130 83
  
 0.313     
 99 59 118 40 59
    67 36 146 72
    75 41 145 65
  
 0.625     
 87 53 165 63 49
    120r 87 85 24
    99 68 105 36
  
1.25      
 86 27 239 93 154*
    64 37 476 247
    63 31 228 121
Positive Control 3-Methylcholanthrene 
2.5       
 43 26 649 501 457*
    45 29 760 561
    42 25 394 310

Induced S9 Trial: 2 Experiment Call: Negative
  Conc.
ug/mL 		Cloning
Efficiency 		Relative Total
Growth 		Mutant Colonies Mutant Frequency Avg Mutant Frequency
Vehicle Control Dimethyl Sulfoxide 
 0         
 127r 114 189 50 46
    107 109 133 42
    86 92 113 44
    101 99 158 52
Test Chemical 2-Mercaptobenzimidazole 
 0.75      
 115 89 138 40 40
    119 96 143 40
    119 91 143 40
  
1         
 120r 101 90 25 42
    87 69 115 44
    114 101 136 40
  
1.5       
 121r 86 121 33
    104 102 103 33
    122r 89 120 33
  
2         
 117 91 145 41 46
    121r 85 179 49
    101 69 153 51
  
3         
 107 90 104 32 41
    106 83 158 50
    110 67 132 40
  
4         
 132r 72 107 27
    124r 92 124 33
    104 95 106 34
Positive Control 3-Methylcholanthrene 
2.5       
 103 71 807 262 244*
    102 86 782 256
    108 74 694 215

Induced S9 Trial: 3 Experiment Call: Inconclusive
  Conc.
ug/mL 		Cloning
Efficiency 		Relative Total
Growth 		Mutant Colonies Mutant Frequency Avg Mutant Frequency
Vehicle Control Dimethyl Sulfoxide 
 0         
 95 146 118 41 38
    82 84 93 38
    74 84 72 32
    72 86 84 39
Test Chemical 2-Mercaptobenzimidazole 
3         
 108 91 142 44 50
    95 94 127 44
    76 77 142 62
  
4         
 85 100 117 46 57*
    72 93 152 71
    89 84 149 56
  
5         
 105 72 93 29 38
    101 87 115 38
    64 77 89 46
  
6         
 85 84 93 37 48
    85 74 144 56
    85 81 127 50
  
8         
 98 102 108 37 34
    85 86 102 40
    120 107 88 24
  
10         
 108 87 144 45 47
    105 86 179 57
    81# 95 95 39
Positive Control 3-Methylcholanthrene 
2.5       
 77 96 568 246 298*
    70 59 681 323
    65 76 634 325

Induced S9 Trial: 4 Experiment Call: Inconclusive
  Conc.
ug/mL 		Cloning
Efficiency 		Relative Total
Growth 		Mutant Colonies Mutant Frequency Avg Mutant Frequency
Vehicle Control Dimethyl Sulfoxide 
 0         
 105 104 102 32 39
    96 93 132 46
    119 100 151 42
    115# 104 115 33
Test Chemical 2-Mercaptobenzimidazole 
5         
 117 122 122 35 32
    101 117 121 40
    117 133 79 23
  
10         
 108 120 135 42 33
    84 66 76 30
    110 121 85 26
  
20         
 112# 148 123 37 32
    116 118 92 26
    107 94 108 34
  
30         
 111 39 123 37 37
    117 106 117 33
    97 69 119 41
  
40         
 104 86 112 36 31
    118 115 98 28
    113 82 96 28
  
50         
 111 27 183 55 46
    110 92 181 55
    113 98 94 28
Positive Control 3-Methylcholanthrene 
2.5       
 99 72 570 193 239*
    112 57 1016 302
    112 57 745 221

Induced S9 Trial: 5 Experiment Call: Negative
  Conc.
ug/mL 		Cloning
Efficiency 		Relative Total
Growth 		Mutant Colonies Mutant Frequency Avg Mutant Frequency
Vehicle Control Dimethyl Sulfoxide 
 0         
 105 80 183 58 52
    111 66 150 45
    111 117 159 48
    102 137 175 57
Test Chemical 2-Mercaptobenzimidazole 
12.5       
 110 161 106 32 36
    102 100 119 39
    115 160 132 38
  
25         
 115 175 91 26 27
    121r 165 153 42
    113 108 97 29
  
50         
 108 186 100 31 38
    116 174 137 39
    101 117 136 45
  
75         
 108 151 107 33 29
    116 88 90 26
    107 142 94 29
  
100         
 104 104 103 33 40
    114 105 156 46
    100 39 123 41
  
150         
 108 47 268 83 65
   
    103 78 144 47
  
200         
   
   
Positive Control 3-Methylcholanthrene 
2.5       
 99 105 782 263 286*
    107 83 857 267
    100 69 980 327

Induced S9 Trial: 6 Experiment Call: Equivocal
  Conc.
ug/mL 		Cloning
Efficiency 		Relative Total
Growth 		Mutant Colonies Mutant Frequency Avg Mutant Frequency
Vehicle Control Dimethyl Sulfoxide 
 0         
 64 86 168 88 70
    91 97 175 64
    97# 107 124 43
    81 110 208 86
Test Chemical 2-Mercaptobenzimidazole 
25         
 88 54 237 90 85
    81 78 215 88
    105 54 238 76
  
50         
 81 82 169 69 67
    99 69 205 69
    98 65 182 62
  
75         
 107 75 175 55 65
    87 72 154 59
    103 58 246 80
  
100         
 84 68 351 140 90
    108 70 214 66
    105 81 202 64
  
150         
 96 76 237 82 74
    112 74 274 82
    114 68 201 59
  
200         
 65 6 238 123 113*
    79 44 313 133
    105 46 260 83
  
300         
   
   
Positive Control 3-Methylcholanthrene 
2.5       
 80 47 722 301 317*
    87 51 872 336
    78 50 739 314

Induced S9 Trial: 7 Experiment Call: Positive
  Conc.
ug/mL 		Cloning
Efficiency 		Relative Total
Growth 		Mutant Colonies Mutant Frequency Avg Mutant Frequency
Vehicle Control Dimethyl Sulfoxide 
 0         
 81 90 75 31 31
    105# 93 103 33
    99# 121 86 29
    105 95 99 31
Test Chemical 2-Mercaptobenzimidazole 
1         
 73 53 61 28 34
    77 46 80 35
    87 38 107 41
  
2         
 105 37 214 68 60*
    79 29 146 62
    78 43 118 51
  
3         
 93 26 175 63 54*
    125r 44 120 32
    79 22 109 46
  
4         
 95 18 117 41 54*
    70 9 122 59
    64 15 119 62
  
5         
 99 10 136 46 41
    109# 11 155 47
    100# 12 92 31
  
7.5       
 60*
    74 8 213 96
    106 15 75 24
  
10         
   
   
Positive Control 3-Methylcholanthrene 
2.5       
 75# 56 423 187 211*
    64 34 411 214
    83 38 581 232

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