AJP - Endocrinology and Metabolism, Vol 268, Issue 4 E572-E579, Copyright © 1995 by American Physiological Society
Sulfation pathway of thyroid hormone metabolism in selenium-deficient male rats
S. Y. Wu, W. S. Huang, I. J. Chopra, M. Jordan, D. Alvarez and F. Santini
Nuclear Medicine and Medical Services, Department of Veterans Affairs Medical Center, Long Beach 90822, USA.
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)
