Sulfation pathway of thyroid hormone metabolism in selenium-deficient male rats.
Male Sprague-Dawley rats were fed a selenium-deficient yeast-based laboratory diet or a control diet for 6 wk. The tissue type I 5'-monodeiodinase (5'-MDI) activity and the immunoassayable 5'-MDI were significantly (P < 0.05) reduced in the liver and the kidney but not in the thyroid of selenium-deficient rats. The mean serum concentrations of thyroxine sulfate (T4S), 3,3',5'-triiodothyronine sulfate (T3S), and reverse T3 sulfate (rT3S) (ng/dl) were significantly increased in selenium-deficient rats (15.7, 59.4, and 22.8, respectively, n = 12) compared with control rats (< 1.0, 18.5, and 9.1, respectively, n = 12, P < 0.01). Kinetic studies were carried out during a constant infusion of unlabeled sulfated iodothyronines (T4S, T3S, or rT3S, n = 5-6/group) at a rate of 1 microgram/h by Alzet minipump for 48 h. The data showed that elevated serum concentrations of T4S or T3S in the selenium-deficient rat are due both to reduced metabolic clearance rate (MCR, mean, l.kg-1.day-1, 7.4 for T4S and 4.5 for T3S in selenium deficiency vs. 12 and 9.2, respectively in controls, P < 0.05) and increased production rate (mean, microgram.kg-1.day-1, 1.2 for T4S, and 2.7 for T3S in selenium deficiency vs. 0.12 and 1.7, respectively, in the controls, P < 0.05). However, the increased serum rT3S concentration in selenium-deficient rats is due mainly to reduced MCR (mean, l.kg-1.day-1, 34 vs. 67 in controls, P < 0.05) and its daily production rate remained unchanged in selenium deficiency (mean, microgram.kg-1.day-1, 7.6 vs. 6.1 in the control group, P > 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)
Wu
S Y
SY
Nuclear Medicine and Medical Services, Department of Veterans Affairs Medical Center, Long Beach 90822, USA.
Huang
W S
WS
Chopra
I J
IJ
Jordan
M
M
Alvarez
D
D
Santini
F
F
D000818:Animals; D001835:Body Weight; D005260:Female; D005979:Glutathione Peroxidase / Q000378:metabolism; D007453:Iodide Peroxidase / Q000378:metabolism; D007700:Kinetics; D008297:Male; D009929:Organ Size; D051381:Rats; D017207:Rats, Sprague-Dawley; D012643:Selenium / Q000172:deficiency*; D012727:Sex Characteristics; D013431:Sulfates / Q000378:metabolism*; D013963:Thyroid Hormones / Q000378:metabolism*; D013970:Thyronines / Q000097:blood / Q000378:metabolism
D013431:Sulfates; D013963:Thyroid Hormones; D013970:Thyronines; D007453:Iodide Peroxidase; D005979:Glutathione Peroxidase; D012643:Selenium