Endocrinology, Vol 113, 306-308, Copyright © 1983 by Endocrine Society
Age affects the generation of serum thyronine-binding protein by rats fed a low protein-high carbohydrate diet
RA Young, R Rajatanavin and LE Braverman
The feeding of a low protein-high carbohydrate (PM) diet to young (8-
week-old) rats induces the production of serum thyronine-binding globulin.
The effect of age on this process was studied in older (5- month-old) rats.
In contrast to the findings in 8-week-old rats, no significant differences
in the serum concentrations of T3 and free T3 and the percentage of free T3
(equilibrium dialysis) were observed between the 5-month-old rats fed the
control diet and those fed the PM diet. There were also no significant
differences between the two diet groups in the distribution of tracer
[125I]T4 and [125I]T3 among the serum proteins as assessed by gel
electrophoresis. The changes in thyronine-binding globulin and subsequent
alterations in T3 binding previously observed in young rats fed a PM diet
do not occur in older rats, suggesting that the age and perhaps the weight
of rats must be considered in studies related to diet-induced effects on
thyroid hormone economy.
