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Study Information
Study Attribute Value
CEBS Accession Number: 002-02966-0004-0000-9
Chemical Name: Trimethoprim
CASRN: 738-70-5
NTP Study Type: Genetic Toxicology - Mammalian Cell Cytogenetics
NTP Study ID: 811628_CA
Study Result: Weakly Positive

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

Trial #:1   Activation: No Activation    Date: 03/24/1984    Harvest Time: 10.5 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 4 0.040 4.0 3 0.030 3.0 0 0.000 0.0 1 0.010 0.0
Dimethyl Sulfoxide 
0         
 100 4 0.040 4.0 3 0.030 3.0 0 0.000 0.0 1 0.010 0.0
Test Chemical: Trimethoprim 
166.7       
 100 4 0.040 3.0 2 0.020 2.0 2 0.020 1.0 0 0.000 0.0 
555         
 100 2 0.020 2.0 1 0.010 2.0 1 0.010 1.0 0 0.000 0.0 
1667         
 100 6 0.060 5.0 2 0.020 2.0 4 0.040 3.0 0 0.000 0.0
Positive Control: Triethylenemelamine 
 0.25      
 100 18 0.180 17.0 10 0.100 10.0 8 0.080 7.0 0 0.000 0.0
Trend: 0.226 -0.454 1.799  
Probability: 0.411 0.675 0.036  


Trial #:1_S9   Activation: Induced Rat Liver S9    Date: 04/02/1981    Harvest Time: 10.5 hour(s)   Trial Call: Weakly 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         
 100 1 0.010 1.0 1 0.010 1.0 0 0.000 0.0 0 0.000 0.0
Dimethyl Sulfoxide 
0         
 100 4 0.040 4.0 3 0.030 3.0 1 0.010 1.0 0 0.000 0.0
Test Chemical: Trimethoprim 
166.7       
 100 0 0.000 0.0 0 0.000 0.0 0 0.000 0.0 0 0.000 0.0 
555         
 100 1 0.010 3.0 0 0.000 0.0 0 0.000 0.0 1 0.010 1.0 
1667         
 92 18 0.196 15.0 2 0.022 2.0 16 0.174 13.0 0 0.000 0.0
Positive Control: Cyclophosphamide 
25         
 100 22 0.220 17.0 16 0.160 13.0 6 0.060 5.0 0 0.000 0.0
Trend: 3.384 -0.676 4.232  
Probability: 0.000 0.751 0.000  


Trial #:2_S9   Activation: Induced Rat Liver S9    Date: 05/08/1981    Harvest Time: 10 hour(s)   Trial Call: Weakly 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         
 100 5 0.050 4.0 5 0.050 5.0 1 0.010 1.0 0 0.000 0.0
Dimethyl Sulfoxide 
0         
 100 10 0.100 7.0 4 0.040 4.0 6 0.060 3.0 0 0.000 0.0
Test Chemical: Trimethoprim 
500         
 100 8 0.080 6.0 5 0.050 5.0 2 0.020 2.0 1 0.010 1.0 
1000         
 100 4 0.040 4.0 4 0.040 4.0 0 0.000 0.0 0 0.000 0.0 
1300         
 100 4 0.040 4.0 1 0.010 1.0 3 0.030 3.0 0 0.000 0.0 
1500         
 100 11 0.110 11.0 1 0.010 1.0 10 0.100 10.0 0 0.000 0.0 
1800         
 100 29 0.290 28.0 3 0.030 3.0 26 0.260 26.0 0 0.000 0.0
Positive Control: Cyclophosphamide 
50         
 100 21 0.210 18.0 18 0.180 16.0 3 0.030 3.0 0 0.000 0.0
Trend: 3.542 -1.529 5.089  
Probability: 0.000 0.937 0.000