Abstract

EFFECTS OF LEAD ON CYTOSOLIC THIOREDOXIN REDUCTASE (TrxR1)
ACTIVITY IN VITRO
Sobieski, R. 1, Conterato, G. M. M. 2 , Somacal, S.1, Augusti, P. R.3, Emanuelli, T.1,
Rocha, J.B.T.2.
1
Departamento de Tecnologia e Ciência dos A limentos, CCR, Universidade Federal
de Santa Maria, Rio Grande do Sul, Brasil; 2Departamento de Química, CCNE,
Universidade Federal de Santa Maria, Rio Grande do Sul, Brasil;
3
Departamento de Bioquímica, ICBS, Universidade Federal do Rio Grande do Sul,
Rio Grande do Sul, Brasil.
Thioredoxin reductase (TrxR1) is an essential antioxidant enzyme. Considering
the possible role of oxidative stress in lead toxicity, the effect of lead on TrxR1 activity
was evaluated in vitro. Adult male Wistar rats were killed and kidneys were removed
to evaluate TrxR1 activity. TrxR1 was time-dependent inhibited after 30, 60 and 120
minutes preincubation with 2000 µM AcPb (75.2±9.4; 51.4±3.6; 17.1±6.1%,
respectively) in comparison with control (p<0.01). TrxR1 activity was stimulated after
120 min preincubation with 0.1 and 1 µM AcPb (124.0±13.7 and 131.8 ± 4.1%,
respectively), but inhibited after preincubation with 500, 1000 and 2000 µM (73.9±0.2,
58.4±3.1 and 17.1±6.1%, respectively) when compared to control (p<0.01). The
amount of inhibition remained the same even after 6 hours of preincubation with 500
µM AcPb (70.3±10.7%, p<0.05). These results suggest that TrxR1 is a potential
target for lead toxicity. These effects of lead on TrxR1 activity in vitro may be involved
in the changes of renal TrxR1 activity observed after exposure of rats in vivo in our
previous study.
Keywords: thioredoxin reductase 1; lead acetate; oxidative stress
Supported by CNPq.