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3811718 
Journal Article 
CHANGES INDUCED BY CADMIUM ADMINISTRATION ON THYROXINE DEIODINATION AND SULFHYDRYL-GROUPS IN RAT-LIVER 
Paier, B; Hagmuller, K; Noli, MI; Pondal, MG; Stiegler, C; Zaninovich, AA 
1993 
Yes 
Journal of Endocrinology
ISSN: 0022-0795
EISSN: 1479-6805 
J ENDOCRINOLOGY LTD 
BRISTOL 
138 
2 
219-224 
English 
8228730 
WOS:A1993MB94000006 
The effects of cadmium on 5'-deiodination of thyroxine
(T4) by rat liver and on the hepatic concentration of non-protein sulfhydryl groups (NPSH) were
studied in Wistar rats of 200-250 g body weight. A group of ten rats was injected with cadmium
chloride (300 mug/100 g body weight i.p.) daily for 4 days. Another group of six rats received,
in addition, dithiothreitol (DTT; 1 mg/100 g body weight i.p.) daily for the same period. A group
of eight normal untreated rats served as control. T4 deiodination was also determined in aliquots
of liver from untreated rats, with cadmium (2 or 5 mmol/l) and with or without DTT (0, 2.5, 5 or
10 mmol/l) plus 1 muCi I-125-labelled T4. Hepatic NPSH were measured by a colorimetric method
employing dithioldinitrobenzoic acid. Homogenates were incubated for 90 min at 37-degrees-C and
chromatographed in a tertiary amyl alcohol : hexane : ammonia (2 mol/l) (10 : 1 : 12) system.
Cadmium-injected rats showed a significant (P<0.01) decrease in T4 deiodination and in the
generation of I-125 (p<0.01) and tri-iodothyronine (T3) (P<0.02). NPSH were also decreased
(P<0.02). Administration of DTT restored T4 deiodination and NPSH to normal. In-vitro addition of
cadmium or DTT to normal rat liver homogenates induced similar effects on the degradation of T4.
Serum concentrations of T4 (P<0.01) and T3 (P<0.01) declined significantly in cadmium-injected
rats, whereas DTT administration failed to normalize serum hormone levels. -The data suggest that
cadmium may have decreased, 5'-deiodinating activity through binding to sulfhydryl groups of
5'-deiodinase as it does in other enzymes. The effects on serum T4 concentrations may be
unrelated to those on 5'-deiodinase.