Akademik Veri Yönetim Sistemi
59th Congress of the European Societies of Toxicology, Athens, Yunanistan, 14 - 17 Eylül 2025, cilt.411, ss.119-120, (Özet Bildiri)
N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine (6-PPD) is an antioxidant
component that has been used for many years to improve the durability and
strength of vehicle tires. However, environmental toxicity of 6-PPD and its
degradation byproduct, 6PPD-quinone, has become a matter of concern since it
was reported to be an environmental contaminant that caused the mass mortality
of coho salmon in 2021. Although the toxic effects of 6-PPD have been studied
in many fish species, including Danio
rerio, the information on its potential effects on amphibians is absent in
the literature. In addition, most of the studies have focused on acute effects,
and knowledge of the subchronic toxicity is still limited. For this purpose,
96-h median lethal concentration (LC50) of 6-PPD was determined in both
zebrafish and Xenopus laevis using
17-day-old larvae to compare the response to 6-PPD toxicity. In addition,
glutathione S-transferase (GST), glutathione reductase (GR) and acetylcholine
esterase (AChE) activities were determined in larvae exposed to LC50/10,
LC50/50 and LC50/100 concentrations of 6-PPD. The LC50s were calculated as 0.589
mg/L and 1.91 mg/L for larval D. rerio
and larval X. laevis, respectively. During
the 21-day exposure period, no mortality was observed in any exposure group of X. laevis larvae. In contrast, for D.
rerio, pronounced toxic effects were observed in larvae for the LC50/10
concentration on day 10 of the experiment, and larvae exposed to the LC50/10
concentration on day 11 died in all containers. GST activity showed a
concentration-dependent induction over the 7-day exposure period for both
species, with enzyme induction ranging from 3-99% for X. laevis and 17-47% for D.
rerio. In contrast, after 21 days of exposure, GST induction ranged from
10-87% in X. laevis, while no
significant increase was observed in zebrafish compared to the control.
Conversely, AChE activity showed no significant response to 6-PPD exposure in either species. GR activity was significantly induced in X. laevis larvae at the LC50/10 exposure
for both 7 and 21 days. The results of the study indicate that D. rerio is more sensitive to 6-PPD
toxicity during the larval developmental stages compared to X. laevis. This sensitivity was evident
in both the LC50 concentrations and lethality levels observed after 21 days of
exposure. The elevated levels of GST, a key detoxification enzyme, and GR, a
key defense mechanism against oxidative stress, in X. laevis compared to D.
rerio may also contribute to the observed higher tolerance in X. laevis larvae. On the other hand, it
is thought that the substance is not effective on an acetylcholine-mediated
stimulus in a possible neurotoxic effect due to 6-PPD toxicity.