Effect of Thyroxine on
Antioxidant Defense System in the Liver of Rats of Different Age
Z. S. SAIČIĆ, D. N. MIJALKOVIĆ, A. L. NIKOLIĆ, D.
P. BLAGOJEVIĆ,
M. B. SPASIĆ
Institute for Biological Research “Siniša Stanković“, Department
of Physiology, Belgrade, Serbia
Received date January 30, 2005
Accepted date October 31, 2005
On-line available December 12, 2005
Summary
The effects of altered thyroid state on the antioxidant defense
system in the liver of differently aged rats were examined. Male
rats aged 15, 45 and 75 days were treated with L-thyroxine, T4
(40 g/100 g body mass, s.c., one dose per day) for 14 days
(finally aged 30, 60 and 90 days, respectively). The following
antioxidant defense enzymes were measured: superoxide dismutases
(both copper zinc, CuZn-SOD and manganese containing, Mn-SOD),
catalase (CAT), glutathione peroxidase (GSH-Px),
glutathione-S-transferase (GST), glutathione reductase (GR), as
well as the content of low molecular mass antioxidant
glutathione (GSH). The effect of T4 on antioxidant defense
system in the liver differs with respect to age. T4 treatment
decreased CAT and GST activities, as well as the content of GSH
in animals aged 60 and 90 days. The same treatment elevated GR
activity in rats at 30 days of age, this phenomenon was not
observed in older animals. The different response of immature
rats to thyroxine compared to older animals could be attributed
to the differences in thyroxine metabolism and the developmental
pattern. Direct effect of T4 on mature rats can be considered as
a part of its overall catabolic action.
Key words
Antioxidant defense enzymes • Glutathione • Liver • Rats •
Thyroxine
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