D. Warshawsky et al., INDUCTION OF MICRONUCLEI AND SISTER-CHROMATID EXCHANGES BY POLYCYCLICAND N-HETEROCYCLIC AROMATIC-HYDROCARBONS IN CULTURED HUMAN-LYMPHOCYTES, Environmental and molecular mutagenesis, 26(2), 1995, pp. 109-118
Many natural environments are contaminated with carcinogenic polycycli
c aromatic hydrocarbons (PAHs) and N-heterocyclic aromatic hydrocarbon
s (NHAs) as complex mixtures of coal tar, petroleum, and shale oil. Th
ese potentially hazardous substances are prevalent at many former tar
production and coal gasification sites. Three polycyclic [benzo(a)pyre
ne (BaP), benz(a)anthracene (BAA), and 7,12-dimethylbenz(a)anthracene
(DMBA)] and two N-heterocyclic [7H-dibenzo(c,g)carbazole (DEC), and di
benz(a,j)acridine (DBA)] aromatic hydrocarbons were analyzed for cytot
oxic and genotoxic effects on human lymphocytes. All of these polyarom
atic compounds are normally present in the environment, except for DMB
A. lymphocytes from healthy donors were isolated from whole blood. The
5-ring polycyclic aromatic BaP consistently induced micronuclei in a
linear dose-dependent manner with doses from 0.1-10.0 mu g/ml, whereas
the 4-ring compounds (BAA and DMBA) had no effect on the induction of
micronuclei above controls except at 5 and 10 mu g/ml. Of the two N-h
eterocyclic compounds, DEC produced a significant increase in micronuc
lei in lymphocytes, but the dose response tended to plateau above 0.1
mu g/ml. DBA showed on effect on the frequency of micronuclei above co
ntrols only at high doses of 5 and 10 mu g/ml. The average background
frequency of micronuclei for 7 lymphocyte donors averaged 3.1 per 1,00
0 stimulated cells, whereas the average frequency of micronuclei at 10
mu g/ml BaP was 36.8 per 1,000 stimulated cells. The lowest effective
dose in 2 donors for BaP occurred at 0.1 mu g/ml. At a challenge dose
of 1 mu g/ml (4 mu M) of BaP, considerable variation in micronuclei i
nduction between 7 individuals was observed, ranging from 2-6-fold inc
reases above spontaneous frequency. Over a dose range of 1-10.0 mu g/m
l (4-40 mu M), BaP also induced sister chromatid exchanges (SCEs) in l
ymphocytes, whereas BAA had no effect above controls. Parallel studies
of both cytogenetic endpoints showed that the micronucleus assay is a
more sensitive indicator of BaP exposure at equivalent doses. Mitotic
and replication indices of BaP-exposed lymphocytes showed that cell p
roliferation is only moderately inhibited even at the highest dose; th
is shows that bulky DNA-adducts are generally compatible with cell sur
vival. The cytogenetic data are consistent, firstoff, with reports tha
t individuals in the population vary widely with respect to the induci
bility of the CYP1A1 gene, which is known to be involved in polycyclic
aromatic hydrocarbon metabolism, in particular, in BaP. Secondly, the
data support the fact that polyaromatic compounds differ with regard
to micronucleus induction within the some sample(s) of human lymphocyt
es, indicating selective metabolism of polyaromatic compounds that may
reflect carcinogen sensitivity of the individual. Thirdly, it would a
ppear that the micronucleus induction in human lymphocytes by PAHs is
an overall-sensitive endpoint for measuring PAH exposure. Lastly, this
is the first report of the use of the micronucleus essay to assess a
series of PAHs and NHAs For their ability to induce genetic damage in
human lymphocytes. (C) 1995 Wiley-Liss, Inc.