AJP - Endocrinology and Metabolism, Vol 247, Issue 4 526-E533, Copyright © 1984 by American Physiological Society
Regulation of hepatic triiodothyronine production in the streptozotocin-induced diabetic rat
A. S. Jennings
The effect of diabetes on 3,5,3'-triiodothyronine (T3) production was
determined in the isolated perfused rat liver. Induction of diabetes with
streptozotocin resulted in decreased serum thyroxine (T4) and T3 levels and
a progressive decline in hepatic T3 production over 5 days. The decline in
T3 production resulted from decreased conversion of T4 to T3, whereas T4
uptake was unchanged. Insulin administration restored serum T4 and T3,
hepatic conversion of T4 to T3, and T3 production to normal levels. When
serum T4 levels in diabetic rats were maintained by T4 administration, the
conversion of T4 to T3 and T3 production returned to control levels.
However, restoration of serum T4 levels in fasted rats failed to correct
the decrease in hepatic T4 uptake or T3 production. Glucagon, at
supraphysiological concentrations in vitro and in vivo, slightly decreased
T4 uptake and T3 production without altering the conversion of T4 to T3.
These data suggest that the fall in serum T4 levels observed in diabetic
rats is important in mediating the decreased hepatic conversion of T4 to T3
and T3 production.
