Propyldazine is mutagenic in Salmonella typhimurium and Escherichia coli: distinct specificity for strains TA1537 and TA97.

The antihypertensive drug propyldazine (Atensil) was demonstrated to be mutagenic with auxotrophic mutants of Salmonella typhimurium and Escherichia coli. Addition of liver S9 mix (postmitochondrial supernatant fraction supplemented with an NADPH-generating system) had little, if any, effect on the mutagenicity. The mutagenicity showed an unusual pattern of strain specificity. Increased frequencies of reversion were observed with all strains whose auxotrophy was caused by frame-shift mutations: the number of revertant colonies per plate from S. typhimurium TA98, TA1538, TA97, and TA1537 was increased up to 5-, 9-, 43-, and 160-fold, respectively, above background. Among the strains that became auxotrophic by substitution mutations, S typhimurium TA102, E. coli WP2, and E coli WP2 uvrA yielded positive results (twofold above background). S. typhimurium TA1535 and TA100 were not reverted by propyldazine. It should be noted that propyldazine, due to its low toxicity and good solubility, could be tested up to very high doses. Hence, although quite impressive mutagenic effects occurred, the mutagenic potency was moderate even in the most responsive strains, TA1537 and TA97 (about 0.3 and 1.0 revertants per nmole, respectively). With the limitation that the strain specificities were different, the mutagenic potency of propyldazine was in the same order of magnitude as that of hydralazine and dihydralazine, two related antihypertensive drugs which were already known to be mutagenic. In our hands, both compounds were mutagenic in S typhimurium TA1535, TA100, TA1537, and TA98. These results differ from data in the literature in that we found clear but weak effects even with strains for which others have reported negative results.