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Study Information
Study Attribute Value
CEBS Accession Number: 002-02669-0004-0000-9
Chemical Name: Phenobarbital
CASRN: 50-06-6
NTP Study Type: Genetic Toxicology - Mammalian Cell Mutagenicity
NTP Study ID: 952103
Study Result: Positive


Table Instructions and Notes:
Studies are indicated to be "Nontoxic" when the observed reductions in relative total growth did not indicate that the maximum tolerated dose was achieved.

Nonactivation Trial: 1 Experiment Call: Inconclusive
  Conc.
ug/mL 		Cloning
Efficiency 		Relative Total
Growth 		Mutant Colonies Mutant Frequency Avg Mutant Frequency
Vehicle Control Acetone 
 0         
 105 94 116 37 35
    95 102 92 32
    93 104 103 37
Test Chemical Phenobarbital 
31.3       
 79# 86 72 31
  
62.5       
 59 65 57 32 32
    91 71 94 34
    80 75 73 31
  
125         
 67# 70 52 26 36
    58# 59 81 46
  
250         
 72 65 71 33 35
    94 72 122 43
    90 90 74 28
  
500         
 85# 59 89 35 38
    76# 67 78 34
    79 71 109 46
  
1000         
 70 58 91 44 39
    87 42 92 35
Positive Control Ethyl Methane Sulfonate 
250         
 74 36 910 409 409*

Nonactivation Trial: 2 Experiment Call: Positive
  Conc.
ug/mL 		Cloning
Efficiency 		Relative Total
Growth 		Mutant Colonies Mutant Frequency Avg Mutant Frequency
Vehicle Control Acetone 
 0         
 70# 104 63 30 29
    62 97 54 29
    66# 95 66 34
    62 104 43 23
Test Chemical Phenobarbital 
250         
 49# 59 20 14 14
    48# 65 19 13
    51# 65 25 17
  
500         
 56# 83 51 30 31
    54 73 51 32
    47 80 43 30
  
750         
 61# 55 80 44 35
    61# 57 45 25
    59 42 65 37
  
1000         
 61# 61 54 30 36
    69 59 73 35
    48 47 60 42
  
1200         
 66# 40 85 43 61*
    53 28 136 86
    57 34 91 53
  
1500         
 61 28 143 79 94*
    69# 57 101 49
    40# 19 186 155
  
2000         
   
   
Positive Control Methyl Methane Sulfonate 
10         
 49# 36 483 330 402*
    28 23 392 475
Methyl Methane Sulfonate 
250         
 79 69 655 278 278*

Nonactivation Trial: 3 Experiment Call: Positive
  Conc.
ug/mL 		Cloning
Efficiency 		Relative Total
Growth 		Mutant Colonies Mutant Frequency Avg Mutant Frequency
Vehicle Control Acetone 
 0         
 83 86 110 44 31
    91# 109 70 26
    87 100 58 22
    96 105 96 33
Test Chemical Phenobarbital 
600         
 81 77 112 46 43
    80 70 102 43
    69 65 84 40
  
800         
 81 49 101 42 42
    69 55 90 43
    79 58 94 40
  
1000         
 92 46 124 45 49*
    78 45 124 53
    80 49 117 49
  
1250         
 80 49 130 54 54*
    86 49 127 49
    86 44 151 58
  
1500         
 66 34 130 65 72*
    74 29 146 65
    65 25 164 85
  
2000         
   
   
Positive Control Methyl Methane Sulfonate 
5         
 74 77 345 156 189*
    61 51 407 222
Methyl Methane Sulfonate 
10         
 36 16 375 349 361*
    50 32 561 373

Induced S9 Trial: 1 Experiment Call: Negative
  Conc.
ug/mL 		Cloning
Efficiency 		Relative Total
Growth 		Mutant Colonies Mutant Frequency Avg Mutant Frequency
Vehicle Control Acetone 
 0         
 67 118 55 27 31
    71# 84 78 37
    87 101 62 24
    66 96 70 35
Test Chemical Phenobarbital 
200         
 67 69 75 37 32
    69 73 64 31
    63 81 51 27
  
400         
 57# 81 58 34 30
    66 73 62 31
    67 85 48 24
  
500         
 69 83 52 25 29
    78 89 66 28
    69# 73 68 33
  
600         
 66 65 62 31 31
    56 63 48 28
    58 68 56 32
  
800         
 64 41 106 55 42
    54 55 60 37
    72 57 70 32
Positive Control 3-Methylcholanthrene 
2.5       
 97# 69 534 184 179*
    84 77 471 188
    96 61 473 165

Footnotes:
Asterisks(*) indicate significant responses.
r = rejected value due to quality control criteria
# = reduced sample size because of the loss of one culture dish due to contamination