[Zinc inhibits the in vitro conversion of thyroxine to triiodothyronine in brown adipose issue].
The effect of in vitro addition of zinc sulphate on T4 deiodination in brown adipose tissue (BAT) of rats exposed to 4 degrees C or 22 degrees C temperature during 24 h, was studied. Animals were killed by cervical dislocation and BAT was immediately removed and homogenized in sucrose buffer (320 mM) containing HEPES (10 mM) pH 7.4. The preparation was centrifuged at 4 degrees C during 10 min. Aliquots were separated adding 50, 100 microM, 1 o 5 mM zinc sulphate plus 0, 5, 10 or 25 mM dithiothreitol plus 1 microCi 125I-T4. The mixture was incubated at 37 degrees C during 60 min. Aliquots were applied to Whatman paper and chromatographed. BAT from control rats kept at 22 degrees C produced 79 +/- 30 pg T3/g protein/h. This value was significantly reduced in homogenates containing 1 or 5 mM zinc. In rats exposed to 4 degrees C, T3 production increased to 248 +/- 37 pg/mg protein/h. The addition of 100 microM, 1 or 5 mM zinc significantly decreased T3 production. The inhibitory action of zinc on BAT T4 deiodination may have a deleterious effect on BAT thermogenesis.
Pavia
M
M
Departamento de Zoología, Universidad de Graz, Austria.
Paier
B
B
Hagmüller
K
K
Zaninovich
A A
AA
D002001:Adipose Tissue, Brown / Q000187:drug effects* / Q000378:metabolism*; D000818:Animals; D066298:In Vitro Techniques; D051381:Rats; D017208:Rats, Wistar; D013696:Temperature; D013974:Thyroxine / Q000378:metabolism*; D014284:Triiodothyronine / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D019287:Zinc Sulfate / Q000494:pharmacology*
D014284:Triiodothyronine; D019287:Zinc Sulfate; D013974:Thyroxine
El cinc inhibe la conversión de tiroxina en triiodotironina en grasa parda in vitro.