Male Wistar rats were injected i.p. 2.5 or 5.0 μg thyroxine (T4) and the level of several iodothyronines and TSH in plasma or biliary excretion of
iodothyronines were estimated by radioimmunoassay in groups of animals in various
intervals up to 144 hr after the administration. In general, two peaks in the plasma
level and biliary excretion of iodothyronines were found: first one within 24 hr and
a delayed second one between about 48 and 72 hr after the administration. It was concluded
that the first peak may correspond to the metabolic changes in fast tissue pools,
while a second one might reflect some delayed iodothyronine metabolic steps in slow
tissue pools after a bolus injection of T.
Thyroid Hormones - Metabolism - Liver - Bile - Plasma
