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Study Information
Study Attribute Value
CEBS Accession Number: 002-01341-0002-0000-3
Chemical Name: 2-Mercaptobenzimidazole
CASRN: 583-39-1
NTP Study Type: Genetic Toxicology - Mammalian Cell Cytogenetics
NTP Study ID: 550909_CA
Study Result: Positive

Study Result: Positive
Activation Trial Trial Call
No Activation  1  Negative 
Induced Rat Liver S9  1_S9  Questionable 
No Activation  2  Negative 
Induced Rat Liver S9  2_S9  Positive 

Trial #:1   Activation: No Activation    Date: 10/16/1984    Harvest Time: 20.5 hour(s)   Trial Call: Negative   
  Dose
µg/mL		 Total
Cells Examined		 Total Aberrations Complex Aberrations Simple Aberrations Other Abs
No. of
Abs		 Abs
Per
Cell		 % Cells
With
Abs		 No. of
Abs.		 Abs
Per
Cell		 % Cells
With
Abs		 No. of
Abs.		 Abs
Per
Cell		 % Cells
With
Abs		 No. of
Abs.		 Abs
Per
Cell		 % Cells
With
Abs
Vehicle Control: Negative (Not Specified) 
0         
 100 1 0.010 1.0 0 0.000 0.0 1 0.010 1.0 0 0.000 0.0
Dimethyl Sulfoxide 
0         
 100 0 0.000 0.0 0 0.000 0.0 0 0.000 0.0 0 0.000 0.0
Test Chemical: 2-Mercaptobenzimidazole 
248.5       
 100 2 0.020 2.0 1 0.010 1.0 1 0.010 1.0 0 0.000 0.0 
300         
 100 2 0.020 2.0 1 0.010 1.0 1 0.010 1.0 0 0.000 0.0 
350         
 100 1 0.010 1.0 1 0.010 1.0 0 0.000 0.0 0 0.000 0.0 
400         
 0 0 0.000 0.0 0 0.000 0.0 0 0.000 0.0 0 0.000 0.0
Positive Control: Mitomycin-C 
 0.04      
 100 20 0.200 17.0 11 0.110 10.0 9 0.090 7.0 0 0.000 0.0
Mitomycin-C 
 0.065     
 25 19 0.760 48.0 11 0.440 32.0 8 0.320 28.0 0 0.000 0.0
Trend: 0.604 0.771 0.008  
Probability: 0.273 0.220 0.497  


Trial #:1_S9   Activation: Induced Rat Liver S9    Date: 07/17/1984    Harvest Time: 10.5 hour(s)   Trial Call: Questionable   
  Dose
µg/mL		 Total
Cells Examined		 Total Aberrations Complex Aberrations Simple Aberrations Other Abs
No. of
Abs		 Abs
Per
Cell		 % Cells
With
Abs		 No. of
Abs.		 Abs
Per
Cell		 % Cells
With
Abs		 No. of
Abs.		 Abs
Per
Cell		 % Cells
With
Abs		 No. of
Abs.		 Abs
Per
Cell		 % Cells
With
Abs
Vehicle Control: Negative (Not Specified) 
0         
 100 2 0.020 2.0 0 0.000 0.0 2 0.020 2.0 0 0.000 0.0
Dimethyl Sulfoxide 
0         
 100 6 0.060 4.0 0 0.000 0.0 5 0.050 3.0 1 0.010 1.0
Test Chemical: 2-Mercaptobenzimidazole 
1500         
 100 17 0.170 14.0 10 0.100 9.0 7 0.070 7.0 0 0.000 0.0 
2000         
 100 12 0.120 11.0 8 0.080 7.0 4 0.040 4.0 0 0.000 0.0 
4000         
 100 5 0.050 5.0 1 0.010 1.0 3 0.030 3.0 1 0.010 1.0 
5000         
 100 7 0.070 7.0 5 0.050 5.0 1 0.010 1.0 1 0.010 1.0
Positive Control: Cyclophosphamide 
7.5       
 100 7 0.070 7.0 3 0.030 3.0 4 0.040 4.0 0 0.000 0.0
Cyclophosphamide 
37.5       
 50 15 0.300 24.0 7 0.140 12.0 7 0.140 14.0 1 0.020 1.0
Trend: -0.569 -0.036 -1.346  
Probability: 0.715 0.514 0.911  


Trial #:2   Activation: No Activation    Date: 07/17/1984    Harvest Time: 22 hour(s)   Trial Call: Negative   
  Dose
µg/mL		 Total
Cells Examined		 Total Aberrations Complex Aberrations Simple Aberrations Other Abs
No. of
Abs		 Abs
Per
Cell		 % Cells
With
Abs		 No. of
Abs.		 Abs
Per
Cell		 % Cells
With
Abs		 No. of
Abs.		 Abs
Per
Cell		 % Cells
With
Abs		 No. of
Abs.		 Abs
Per
Cell		 % Cells
With
Abs
Vehicle Control: Negative (Not Specified) 
0         
 100 1 0.010 1.0 0 0.000 0.0 1 0.010 1.0 0 0.000 0.0
Dimethyl Sulfoxide 
0         
 100 3 0.030 3.0 1 0.010 1.0 1 0.010 1.0 1 0.010 1.0
Test Chemical: 2-Mercaptobenzimidazole 
200         
 100 0 0.000 0.0 0 0.000 0.0 0 0.000 0.0 0 0.000 0.0 
250         
 0 0 0.000 0.0 0 0.000 0.0 0 0.000 0.0 0 0.000 0.0 
300         
 0 0 0.000 0.0 0 0.000 0.0 0 0.000 0.0 0 0.000 0.0 
350         
 100 4 0.040 4.0 1 0.010 1.0 1 0.010 1.0 2 0.020 2.0 
400         
 100 2 0.020 2.0 1 0.010 1.0 0 0.000 0.0 1 0.010 1.0 
500         
 0 0 0.000 0.0 0 0.000 0.0 0 0.000 0.0 0 0.000 0.0
Positive Control: Mitomycin-C 
 0.025     
 100 20 0.200 17.0 9 0.090 9.0 10 0.100 8.0 1 0.010 1.0
Mitomycin-C 
 0.063     
 25 14 0.560 48.0 8 0.320 32.0 6 0.240 24.0 0 0.000 0.0
Trend: 0.613 0.421 -0.305  
Probability: 0.270 0.337 0.620  


Trial #:2_S9   Activation: Induced Rat Liver S9    Date: 07/25/1984    Harvest Time: 10.5 hour(s)   Trial Call: Positive   
  Dose
µg/mL		 Total
Cells Examined		 Total Aberrations Complex Aberrations Simple Aberrations Other Abs
No. of
Abs		 Abs
Per
Cell		 % Cells
With
Abs		 No. of
Abs.		 Abs
Per
Cell		 % Cells
With
Abs		 No. of
Abs.		 Abs
Per
Cell		 % Cells
With
Abs		 No. of
Abs.		 Abs
Per
Cell		 % Cells
With
Abs
Vehicle Control: Negative (Not Specified) 
0         
 50 1 0.020 2.0 1 0.020 2.0 0 0.000 0.0 0 0.000 0.0
Dimethyl Sulfoxide 
0         
 50 2 0.040 4.0 0 0.000 0.0 1 0.020 2.0 1 0.020 2.0
Test Chemical: 2-Mercaptobenzimidazole 
1750         
 50 26 0.520 38.0 0 0.000 0.0 26 0.520 38.0 0 0.000 0.0 
2000         
 50 18 0.360 32.0 1 0.020 2.0 16 0.320 28.0 1 0.020 2.0 
2250         
 50 25 0.500 40.0 6 0.120 12.0 19 0.380 32.0 0 0.000 0.0
Positive Control: Cyclophosphamide 
7.5       
 50 4 0.080 8.0 0 0.000 0.0 3 0.060 6.0 1 0.020 2.0
Cyclophosphamide 
37.5       
 25 15 0.600 44.0 3 0.120 12.0 11 0.440 32.0 1 0.040 4.0
Trend: 3.565 3.232 2.916  
Probability: 0.000 0.001 0.002