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5146391 
Journal Article 
Binary Mixtures Containing Isomers of Nitrobenzo(a)pyrene Induce Greater-than-Additive Mutational Responses in Salmonella typhimurium. I. Analysis by the Total Concentration-Proportional Mixture Model 
Hass, BS; Chen, JJ; Chou, MW; Fu, PP; Heflich, RH 
1987 
1 
Mutation Research
ISSN: 0027-5107
EISSN: 1873-135X 
190 
4 
247-252 
English 
3550451 
The mutagenicities of binary mixtures of 1-nitrobenzo(a)pyrene (70021997) (1-NBP) and 3-nitrobenzo(a)pyrene (3-NBP) in Salmonella-typhimurium were studied at a total hydrocarbon concentration of 0.40 micrograms/plate. As significant nonadditive mutagenic responses were obtained with these 1-NBP/3-NBP mixtures, tests were also made on other pairs of isomers such as 1-NBP and 6-nitrobenzo(a)pyrene (63041907) (6-NBP) and 3-NBP and 6-NBP. Mixtures of either 1-NBP or 3-NBP with benzo(a)pyrene (50328) (BP) were also tested. The total concentration/proportional mixture method was used for data evaluation. A graphical presentation of the results of measuring the number of revertants per plate induced by 0.40 micrograms/plate of the individual chemicals was made. A comparison of this graph with revertants caused by binary mixtures of these compounds demonstrated a greater than additive response to the mixtures relative to the individual components. This finding was confirmed by the analysis of the model coefficients of b1 (associated with background mutational responses), b2 (related to individual component responses), and b12. The coefficient values of b1 revealed a positive direct mutagenic responsiveness of 1-NBP, while values for 6-NBP and BP were similar to controls. Values of b2 reflected positive direct acting responses for 1-NBP or 3-NBP. Based on the value of the coefficient b12, for each combination of the two NBPs, a greater than additive response was obtained. Synergistic responses were less apparent at lower total hydrocarbon concentrations, suggesting a dose response effect for these interactions. It also appeared that the more mutagenic of any two components had more impact on the overall response. Mixtures containing BP showed different interactions than those in which two nitrobenzo(a)pyrenes were included. 
(Salmonella typhimurium); binary mixtures; Concentration/proportional mixture model; Mutational response; Nitrobenzo[a]pyrene