ACTIVATION OF ARYLAMINES TO MUTAGENIC PRODUCT(S) BY 2 IN-VITRO PLANT-SYSTEMS

Plant activation of three isomers of phenylenediamine, o-, rn-and p-ph enylenediamine, has been studied. Two in vitro plant systems have been used: Persea americana S117 with mixed-function oxidase (MFO) and per oxidase activities, and Zea mays S9 which contains only peroxidase act ivity. As genetic endpoint, the classical Salmonella tester strains, T A98 and TA100, their derivatives with high O-acetyltransferase levels (YG102 and YG1029, respectively) and TA98/1,8-DNP6, deficient in this enzyme, have been assayed. Of the three isomers studied, only m-PDA wa s activated to mutagenic product(s) by both plant systems. This activa tion required the bacterial O-acetyltransferase activity to give frame shift mutagenic product(s), detected in TA98 and YG1024 strains. In al l the assays the P. americana system was more potent than the Z. mays system in activating m-PDA. A slight increase of the number of YG1029 revertants was detected when m-PDA was activated by P. americana, sugg esting that this compound can be also converted into ultimate mutageni c product(s) that induce base-pair substitutions. m-PDA activation by Z. mays was dependent on the peroxidase activity of this system, but t he activation produced by P. americana was totally dependent on MFOs, because a total inhibition of the mutagenic response was found when th ese activities were inhibited. In addition, the P. americana System wa s more potent in generating proximal mutagenic forms from m-PDA than S 9 from non-induced rat liver, although S9 from Aroclor 1254-induced Sp rague-Dawley male rats was the most potent system in the m-PDA activat ion. These results indicate that the P. americana system can be useful in determining the role of mixed-function oxidases in plant activatio n of xenobiotics. (C) 1997 Elsevier Science B.V.