Thyroxine 5'-deiodination in brown adipose tissue and pineal gland: implications for thermogenic regulation and role of melatonin.
T4 type II 5'-deiodinase (5'-D II) activity was studied in wild-captured Richardson's ground squirrels. As previously reported for other species, 5'-D II activity was detected in frontal cortex, cerebellum, pineal gland, and brown adipose tissue (BAT); in the median eminence the levels of 5'-D II activity were undetectable with our methodology. When pineal gland, frontal cortex, and cerebellum nyctohemeral profiles were studied, none of them showed variations. Cold exposure for 4 h led to an increase in the enzymatic activity 10-fold above the basal values for BAT, while in the pineal gland the values were doubled; cold exposure failed to change the 5'-D II activity in the frontal cortex. Acute melatonin treatment caused a 7-fold increase in 5'-D II activity in BAT, but did not affect enzyme activity in either the pineal gland or frontal cortex. The data indicate that 5'-D II in Richardson's ground squirrel shows classical localizations. Additionally, two new regulatory factors of 5'-D II are reported, i.e. melatonin for BAT and cold for the pineal gland.
Puig-Domingo
M
M
Department of Cellular and Structural Biology, University of Texas Health Science Center, San Antonio 78284.
Guerrero
J M
JM
Reiter
R J
RJ
Tannenbaum
M J
MJ
Hurlbut
E C
EC
Gonzalez-Brito
A
A
Santana
C
C
D002001:Adipose Tissue, Brown / Q000187:drug effects / Q000201:enzymology*; D000818:Animals; D001833:Body Temperature Regulation; D002531:Cerebellum / Q000187:drug effects / Q000201:enzymology; D002540:Cerebral Cortex / Q000187:drug effects / Q000201:enzymology; D003080:Cold Temperature; D005260:Female; D007453:Iodide Peroxidase / Q000378:metabolism*; D007457:Iodine Radioisotopes; D008297:Male; D008473:Median Eminence / Q000187:drug effects / Q000201:enzymology; D008550:Melatonin / Q000502:physiology*; D008713:Methimazole / Q000494:pharmacology; D010870:Pineal Gland / Q000201:enzymology*; D012589:Sciuridae / Q000378:metabolism*; D013974:Thyroxine / Q000378:metabolism
D007457:Iodine Radioisotopes; D008713:Methimazole; D007453:Iodide Peroxidase; D008550:Melatonin; D013974:Thyroxine