An analysis of weak mutagens in the Ames assay.

Nitrosopiperidine, sodium nitrite and 1,2 epoxybutane were tested in the Ames agar incorporation assay in an attempt to establish exact criteria for detecting the activity of these weak mutagens. As regards minimum concentrations it was determined that at 500 microgram per plate a statistical analysis and several concentrations of the activating system are required in order to manifest an indication of the mutagenicity of 1,2 epoxybutane. The mutagenicity of sodium nitrite was detectable at 80 microgram/plate while nitrosopiperidine produced a 2.5-3.2 increase over background at 250 microgram/plate. It is concluded that since weak mutagenicity cannot be predicted it is advisable to utilize the maximum concentrations possible within the limits of solubility and bacterial toxicity. At the higher concentrations 1,2 epoxybutane, nitrosopiperidine and sodium nitrite produced revertant colony counts equal to 7, 17 and 62 times above background, respectively.