Thyroid and pituitary thyroxine-5'-deiodinase activity and thyrotrophin secretion in lithium-treated rats.
Some authors have reported increased serum thyrotrophin (TSH) in animals chronically treated with lithium, suggesting that lithium might decrease pituitary thyroxine (T(4))-5'-deiodinase activity. On the other hand, the effect of lithium treatment on thyroidal T(4)-5'-deiodinase activity is also unknown. The present study was undertaken to evaluate the effects of lithium treatment on pituitary and thyroid T(4)-5'-deiodinase activity. Serum and pituitary TSH levels and thyroidal and pituitary T(4)-5'-deiodinase activities were determined in 3-month-old isogenic male Dutch-Miranda rats treated with lithium for 8 weeks. Chronic lithium treatment produced a slight increase in pituitary TSH content, but no change in serum TSH, and a significant increase in the thyroidal T(4)-5'-deiodinase activity. However, the pituitary T(4)-5'-deiodinase activity was unaffected by lithium administration. As far as we know, the present data show for the first time that chronic lithium treatment can increase the thyroxine to tri-iodothyronine conversion in the murine thyroid gland, be it directly or indirectly.
Frankenfeld
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TG
Laboratório de Fisiologia Endócrina, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Centro de Ciencias da Saude, Cidade Universitária, 21949.900-Rio de Janeiro, Brasil.
Corrêa Da Costa
V M
VM
Nascimento-Saba
C C A
CC
Ortiga-Carvalho
T M
TM
Santos
R M M
RM
Lisboa
P C
PC
Carvalho
D P
DP
Rosenthal
D
D
D000704:Analysis of Variance; D000818:Animals; D007453:Iodide Peroxidase / Q000032:analysis / Q000378:metabolism*; D007527:Isoenzymes / Q000032:analysis / Q000378:metabolism*; D008094:Lithium / Q000494:pharmacology*; D008297:Male; D010902:Pituitary Gland / Q000187:drug effects / Q000201:enzymology*; D051381:Rats; D011919:Rats, Inbred Strains; D013961:Thyroid Gland / Q000187:drug effects / Q000201:enzymology*; D013972:Thyrotropin / Q000378:metabolism*
D007527:Isoenzymes; D013972:Thyrotropin; D008094:Lithium; D007453:Iodide Peroxidase