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Study Information
Study Attribute Value
CEBS Accession Number: 002-02669-0001-0000-6
Chemical Name: Phenobarbital
CASRN: 50-06-6
NTP Study Type: Genetic Toxicology - Mammalian Cell Cytogenetics
NTP Study ID: 539978_SCE
Study Result: Negative

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

Trial #: 1    Activation: No Activation    Date: 01/13/1983    Trial Call: Negative   
  Dose
µg/mL		 Number
Cells
Examined		 Number
Chromosomes
Examined		 Total
Number
SCEs		 SCE /
Chromosome		 SCE /
Cell		 Hours in
BRDU		 % Increase
Over Solvent
Control
Vehicle Control Dimethyl Sulfoxide 
0         
 50 1046 414 0.396 8.28 26.0 0.000
Negative (Not Specified) 
0         
 50 1052 419 0.398 8.38 26.0 0.630
Test Chemical Phenobarbital 
16         
 50 1044 410 0.393 8.20 26.0 -0.776 
50         
 50 1046 470 0.449 9.40 26.0 13.527 
160         
 50 1043 428 0.410 8.56 26.0 3.679 
500         
 50 1042 498 0.478 9.96 26.0 20.752 
1600         
 0 0 0 0.000 0.00 30.0 N/A
Positive Control Mitomycin-C 
 0.01      
 50 1042 1936 1.858 38.72 26.0 369.428
Trend: 2.843        
Probability: 0.002        

Trial #: 2    Activation: No Activation    Date: 02/28/1983    Trial Call: Negative   
  Dose
µg/mL		 Number
Cells
Examined		 Number
Chromosomes
Examined		 Total
Number
SCEs		 SCE /
Chromosome		 SCE /
Cell		 Hours in
BRDU		 % Increase
Over Solvent
Control
Vehicle Control Dimethyl Sulfoxide 
0         
 50 1042 393 0.377 7.86 26.0 0.000
Negative (Not Specified) 
0         
 50 1034 405 0.392 8.10 26.0 3.851
Test Chemical Phenobarbital 
250         
 50 1032 495 0.480 9.90 37.0 27.175 
500         
 50 1034 436 0.422 8.72 37.0 11.800 
1000         
 0 0 0 0.000 0.00 37.0 N/A 
1500         
 0 0 0 0.000 0.00 37.0 N/A 
2000         
 0 0 0 0.000 0.00 37.0 N/A
Positive Control Mitomycin-C 
 0.005     
 50 1044 1785 1.710 35.70 26.0 353.328
Trend: 1.290        
Probability: 0.098        

Trial #: 1_S9    Activation: Induced Rat Liver S9    Date: 01/13/1983    Trial Call: Negative   
  Dose
µg/mL		 Number
Cells
Examined		 Number
Chromosomes
Examined		 Total
Number
SCEs		 SCE /
Chromosome		 SCE /
Cell		 Hours in
BRDU		 % Increase
Over Solvent
Control
Vehicle Control Negative (Not Specified) 
0         
 50 1034 422 0.408 8.44 26.0 9.993
Dimethyl Sulfoxide 
0         
 50 1043 387 0.371 7.74 26.0 0.000
Test Chemical Phenobarbital 
16         
 50 1037 381 0.367 7.62 26.0 -0.981 
50         
 50 1054 365 0.346 7.30 26.0 -6.669 
160         
 50 1043 389 0.373 7.78 26.0 0.517 
500         
 50 1049 415 0.396 8.30 26.0 6.622 
1600         
 50 1037 452 0.436 9.04 30.0 17.472
Positive Control Cyclophosphamide 
1.5       
 50 1044 1094 1.048 21.88 26.0 182.417
Trend: 2.721        
Probability: 0.003        

Trial #: 2_S9    Activation: Induced Rat Liver S9    Date: 02/08/1983    Trial Call: Negative   
  Dose
µg/mL		 Number
Cells
Examined		 Number
Chromosomes
Examined		 Total
Number
SCEs		 SCE /
Chromosome		 SCE /
Cell		 Hours in
BRDU		 % Increase
Over Solvent
Control
Vehicle Control Negative (Not Specified) 
0         
 50 1041 416 0.400 8.32 26.0 3.622
Dimethyl Sulfoxide 
0         
 50 1045 403 0.386 8.06 26.0 0.000
Test Chemical Phenobarbital 
1000         
 50 1045 407 0.389 8.14 26.0 0.993 
2000         
 50 1037 419 0.404 8.38 26.0 4.772 
3000         
 50 1039 452 0.435 9.04 26.0 12.807 
4000         
 50 1041 428 0.411 8.56 26.0 6.612
Positive Control Cyclophosphamide 
1.5       
 50 1045 1246 1.192 24.92 26.0 209.181
Trend: 1.642        
Probability: 0.050