Endocrinology, Vol 110, 1607-1612, Copyright © 1982 by Endocrine Society
Low protein-high carbohydrate diet induces alterations in the serum thyronine-binding proteins in the rat
RA Young, LE Braverman and R Rajatanavin
The serum T3 concentration was increased in 8-week-old lean Zucker rats fed
a low protein-high carbohydrate diet for 2 weeks. This increase was
secondary to the generation of a binding protein migrating in the
postalbumin zone in polyacrylamide gel electrophoresis employing 125I-
labeled T3 and is termed rat thyronine-binding globulin. The presence of
this T3-binding protein in serum resulted in a marked decrease in the
percent free T3 assessed by equilibrium dialysis and a normal free T3
concentration. An increase in the binding of T4 in the postalbumin zone was
also observed, but no changes in the dialyzable fraction of T4 or the total
and free T4 concentrations occurred. In contrast to these findings in lean
Zucker rats fed the low protein-high carbohydrate diet, no change in the
pattern of 125I-labeled T3 and T4 binding, the dialyzable fraction of T3 or
T4, or total and free T3 or T4 concentrations were observed in the obese
Zucker rats fed this diet. The present findings suggest that diet-induced
alterations in thyroid hormone-binding proteins must be considered in the
interpretation of data which involve alterations in total thyroid hormone
concentrations in serum and their role in affecting tissue metabolism.
