Changes induced by cadmium administration on thyroxine deiodination and sulfhydryl groups in rat liver.
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 micrograms/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 microCi 125I-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 125I (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.(ABSTRACT TRUNCATED AT 250 WORDS)
Paier
B
B
Department of Zoology, University of Graz, Austria.
Hagmüller
K
K
Noli
M I
MI
Gonzalez Pondal
M
M
Stiegler
C
C
Zaninovich
A A
AA
D000818:Animals; D002104:Cadmium / Q000494:pharmacology*; D019256:Cadmium Chloride; D002712:Chlorides / Q000494:pharmacology*; D004228:Dithionitrobenzoic Acid / Q000494:pharmacology; D004229:Dithiothreitol / Q000494:pharmacology; D066298:In Vitro Techniques; D007453:Iodide Peroxidase / Q000378:metabolism*; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D013438:Sulfhydryl Compounds / Q000378:metabolism*; D013974:Thyroxine / Q000097:blood / Q000378:metabolism*; D014284:Triiodothyronine / Q000097:blood
D002712:Chlorides; D013438:Sulfhydryl Compounds; D002104:Cadmium; D014284:Triiodothyronine; D004228:Dithionitrobenzoic Acid; D007453:Iodide Peroxidase; D019256:Cadmium Chloride; D013974:Thyroxine; D004229:Dithiothreitol