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Study Information
Study Attribute Value
CEBS Accession Number: 002-02631-0001-0000-5
Chemical Name: Parathion
CASRN: 56-38-2
NTP Study Type: Genetic Toxicology - Mammalian Cell Cytogenetics
NTP Study ID: 580599_SCE
Study Result: Positive

Study Result: Positive
Activation Trial Trial Call
No Activation  1  Negative 
Induced Rat Liver S9  1_S9  Test Failure 
Induced Rat Liver S9  2_S9  Positive 
Induced Rat Liver S9  3_S9  Positive 

Trial #: 1    Activation: No Activation    Date: 01/04/1983    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 1009 445 0.441 8.90 25.5 0.000
Test Chemical Parathion 
12.7       
 50 1029 487 0.473 9.74 34.5 7.311 
25.4       
 50 1014 454 0.448 9.08 34.5 1.519 
50.8       
 50 1017 504 0.496 10.08 34.5 12.368 
101.6       
 0 0 0 0.000 0.00 0.0 N/A
Positive Control Mitomycin-C 
 0.001     
 50 1024 654 0.639 13.08 25.5 44.813
Mitomycin-C 
 0.01      
 5 103 217 2.107 43.40 25.5 377.698
Trend: 1.441        
Probability: 0.075        

Trial #: 1_S9    Activation: Induced Rat Liver S9    Date: 12/28/1982    Trial Call: Test Failure   
  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 1032 435 0.422 8.70 25.5 0.000
Test Chemical Parathion 
40.3       
 50 1033 453 0.439 9.06 25.5 4.037 
121         
 13 263 127 0.483 9.77 29.5 14.561
Trend: 1.281        
Probability: 0.100        

Trial #: 2_S9    Activation: Induced Rat Liver S9    Date: 01/04/1983    Trial Call: Positive   
  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 1014 427 0.421 8.54 25.5 0.000
Test Chemical Parathion 
25.4       
 50 1026 519 0.506 10.38 25.5 20.124 
50.8       
 50 1017 472 0.464 9.44 25.5 10.213 
101.6       
 50 1034 533 0.515 10.66 34.5 22.410
Positive Control Cyclophosphamide 
 0.3       
 50 1030 569 0.552 11.38 25.5 31.185
Cyclophosphamide 
2         
 5 104 126 1.212 25.20 25.5 187.705
Trend: 2.496        
Probability: 0.006        

Trial #: 3_S9    Activation: Induced Rat Liver S9    Date: 02/08/1983    Trial Call: Positive   
  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 1023 440 0.430 8.80 25.5 0.000
Test Chemical Parathion 
90         
 50 1032 545 0.528 10.90 25.5 22.783 
110         
 50 1012 555 0.548 11.10 32.3 27.507 
131         
 50 1018 542 0.532 10.84 32.3 23.787 
155         
 0 0 0 0.000 0.00 0.0 N/A
Positive Control Cyclophosphamide 
 0.3       
 50 1026 561 0.547 11.22 25.5 27.127
Cyclophosphamide 
2         
 5 105 156 1.486 31.20 25.5 245.429
Trend: 3.281        
Probability: 0.001