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Study Information
Study Attribute Value
CEBS Accession Number: 002-02343-0008-0000-2
Chemical Name: L-Tryptophan
CASRN: 73-22-3
NTP Study Type: Genetic Toxicology - Mammalian Cell Mutagenicity
NTP Study ID: 304004
Study Result: Equivocal


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: Negative and Non-Toxic
  Conc.
ug/mL 		Cloning
Efficiency 		Relative Total
Growth 		Mutant Colonies Mutant Frequency Avg Mutant Frequency
Vehicle Control Fischer Medium 
 0         
 76 100 110 48 61
    94 103 146 52
    86 100 163 63
    69 96 164 79
Test Chemical L-Tryptophan 
125         
 66 111 100 51 57
    66 88 126 64
  
250         
 70 75 137 66 61
    65 90 112 57
  
500         
 69 99 140 68 70
    76 102 164 72
  
1000         
 103 108 132 43 54
    84 102 162 65
  
2000         
 70 92 110 52 54
    63 85 105 56
Positive Control Methyl Methane Sulfonate 
15         
 36 26 227 210 182*
    60 32 276 153

Nonactivation Trial: 2 Experiment Call: Negative and Non-Toxic
  Conc.
ug/mL 		Cloning
Efficiency 		Relative Total
Growth 		Mutant Colonies Mutant Frequency Avg Mutant Frequency
Vehicle Control Fischer Medium 
 0         
 90 109 89 33 35
    77 99 63 27
    80 95 87 36
    88 97 111 42
Test Chemical L-Tryptophan 
400         
 67 46 67 33 37
    77 30 93 40
  
800         
 77 98 66 28 27
    78 30 60 26
  
1200         
 79 85 104 44 42
    74 82 91 41
  
1600         
 73 65 87 40 37
    71 64 74 35
  
2000         
 80 59 107 45 39
    90 68 89 33
Positive Control Methyl Methane Sulfonate 
15         
 44 36 318 241 230*
    44 35 289 219

Nonactivation Trial: 3 Experiment Call: Negative and Non-Toxic
  Conc.
ug/mL 		Cloning
Efficiency 		Relative Total
Growth 		Mutant Colonies Mutant Frequency Avg Mutant Frequency
Vehicle Control Fischer Medium 
 0         
 90 102 105 39 46
    84 106 126 50
    63 92 90 48
    99 101 137 46
Test Chemical L-Tryptophan 
400         
 82 98 62 25 36
    78 80 109 47
  
800         
 76 89 116 51 56
    80 80 148 62
  
1200         
 75 72 161 72 62
    70 62 109 52
  
1600         
 68 62 105 52 62
    70# 52 150 72
  
2000         
 60 66 120 66 60
    71 64 116 55
Positive Control Methyl Methane Sulfonate 
15         
 19 14 71 125 108*
    32 22 88 91

Induced S9 Trial: 1 Experiment Call: Equivocal
  Conc.
ug/mL 		Cloning
Efficiency 		Relative Total
Growth 		Mutant Colonies Mutant Frequency Avg Mutant Frequency
Vehicle Control Fischer Medium 
 0         
 79 117 187 79 89
    56 84 171 102
    78 106 218 93
    74 93 184 83
Test Chemical L-Tryptophan 
400         
 63 90 198 106 105
    50 89 156 105
  
800         
 41 51 192 155 123
    56 71 152 90
  
1200         
 73 77 182 83 111
    60 73 250 139
  
1600         
 64 71 203 106 117
    48 61 185 128
  
2000         
 46# 52 209 151 154*
    56 63 260 156
Positive Control 3-Methylcholanthrene 
2.5       
 30 26 777 868 768*
    39 27 789 669

Induced S9 Trial: 2 Experiment Call: Positive
  Conc.
ug/mL 		Cloning
Efficiency 		Relative Total
Growth 		Mutant Colonies Mutant Frequency Avg Mutant Frequency
Vehicle Control Fischer Medium 
 0         
 72# 98 97.5 45 30
    76 101 35 15
    83 91 100 40
    79 110 41 17
Test Chemical L-Tryptophan 
1200         
 61 79 106 58 49*
    75 91 92 41
  
1400         
 71 76 127 59 58*
    68 82 116 57
  
1600         
 72 78 124 57 50*
    83 90 106 42
  
1800         
 67 73 117 58 57*
    74 75 126 57
  
2000         
 67 81 103 51 57*
    63 71 118 63
Positive Control 3-Methylcholanthrene 
2.5       
 53 35 375 237 207*
    64 33 339 178

Induced S9 Trial: 3 Experiment Call: Negative
  Conc.
ug/mL 		Cloning
Efficiency 		Relative Total
Growth 		Mutant Colonies Mutant Frequency Avg Mutant Frequency
Vehicle Control Fischer Medium 
 0         
 59 111 26 15 16
    62 94 20 11
    87 99 48 18
    66 95 37 19
Test Chemical L-Tryptophan 
1200         
 69 55 53 26 19
    65 54 24 12
  
1400         
 59 93 34 19 22
    65 89 48 25
  
1600         
 71 86 60 28 23
    66 82 35 18
  
1800         
 78 86 45 19 21
    63 96 42 22
  
2000         
 33 34 17 17 23
    40 29 34 28
Positive Control 3-Methylcholanthrene 
2.5       
 46 20 168 121 137*
    42 43 191 153

Induced S9 Trial: 4 Experiment Call: Negative and Non-Toxic
  Conc.
ug/mL 		Cloning
Efficiency 		Relative Total
Growth 		Mutant Colonies Mutant Frequency Avg Mutant Frequency
Vehicle Control Fischer Medium 
 0         
 75 102 54 24 20
    74# 105 33 15
    74 93 41 19
    92 100 58 21
Test Chemical L-Tryptophan 
1200         
 76 87 39 17 19
    80 84 51 21
  
1400         
 97 94 57 20 20
    81 84 48 20
  
1600         
 54 98 40 25 26
    66 81 56 28
  
1800         
 65 60 38 19 19
    80 79 46 19
  
2000         
 96 76 55 19 19
    81 76 44 18
Positive Control 3-Methylcholanthrene 
2.5       
 62 45 288 154 158*
    55 42 265 162

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