Benznidazole (bz) is a widely used trypanosomicidal agent in South Ame
rica. Two test systems were used to evaluate its genotoxicity in human
cells in vitro: (a) human blood lymphocytes from healthy volunteers f
or induction of sister-chromatid exchanges (SCEs) and chromosomal aber
rations (CAs); (b) a human hepatoma cell line (Hep G2) for the inducti
on of SCEs and micronuclei (MN). In spite of being non-clastogenic on
human lymphocytes, there was a significant increase in the frequency o
f MN on hepatoma cells treated with different doses of bz. This result
s support previous data which indicated the necessity of nitroreductio
n of nitroimidazoles to observe their mutagenic effects. Interestingly
, bz induced a significant increase in the frequency of SCEs in both t
est systems. The sensitivity of the parameters used and the role of ce
llular metabolic pathways are discussed.