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Study Information
Study Attribute Value
CEBS Accession Number: 002-02308-0001-0000-6
Chemical Name: Isobutyl nitrite
CASRN: 542-56-3
NTP Study Type: Genetic Toxicology - Mammalian Cell Cytogenetics
NTP Study ID: 016060_SCE
Study Result: Positive

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

Trial #: 1    Activation: No Activation    Date: 01/30/1990    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 Negative (Not Specified) 
0         
 50 1049 346 0.330 6.92 26.0 -7.398
Dimethyl Sulfoxide 
0         
 50 1050 374 0.356 7.48 26.0 0.000
Test Chemical Isobutyl nitrite 
5         
 50 1048 459 0.438 9.18 26.0 22.961 
17         
 50 1047 469 0.448 9.38 26.0 25.760 
50         
 50 1047 544 0.520 10.88 26.0 45.871 
167         
 0 0 0 0.000 0.00 31.0 N/A
Positive Control Mitomycin-C 
 0.001     
 50 1052 657 0.625 13.14 26.0 75.334
Mitomycin-C 
 0.004     
 10 210 192 0.914 19.20 26.0 156.684
Trend: 5.435        
Probability: 0.000        

Trial #: 2    Activation: No Activation    Date: 03/15/1990    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 1047 384 0.367 7.68 26.0 0.000
Negative (Not Specified) 
0         
 50 1052 366 0.348 7.32 26.0 -5.141
Test Chemical Isobutyl nitrite 
17         
 50 1049 414 0.395 8.28 26.0 7.607 
50         
 50 1047 467 0.446 9.34 26.0 21.615 
100         
 50 1047 526 0.502 10.52 26.0 36.979
Positive Control Mitomycin-C 
 0.001     
 50 1046 637 0.609 12.74 26.0 66.044
Mitomycin-C 
 0.004     
 10 209 183 0.876 18.30 26.0 138.737
Trend: 5.035        
Probability: 0.000        

Trial #: 1_S9    Activation: Induced Rat Liver S9    Date: 01/30/1990    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 1053 405 0.385 8.10 26.0 -4.663
Dimethyl Sulfoxide 
0         
 50 1051 424 0.403 8.48 31.0 0.000
Test Chemical Isobutyl nitrite 
167         
 50 1048 597 0.570 11.94 26.0 41.205 
500         
 50 1051 883 0.840 17.66 31.0 108.255 
1667         
 25 524 563 1.074 22.52 31.0 166.326 
5000         
 0 0 0 0.000 0.00 0.0 N/A
Positive Control Cyclophosphamide 
 0.125     
 50 1049 638 0.608 12.76 26.0 50.759
Cyclophosphamide 
 0.5       
 10 211 214 1.014 21.40 26.0 151.402
Trend: 17.220        
Probability: 0.000