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The uptake of thyroxine and tri‐iodothyronine by perfused hearts
Author(s) -
Hillier A. P.
Publication year - 1969
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1969.sp008885
Subject(s) - hormone , medicine , endocrinology , triiodothyronine , perfusion , thyroid hormones , chemistry , steady state (chemistry) , thyroid , biology
1. An examination has been made of the uptake of radioactive thyroxine and tri‐iodothyronine by the perfused hearts of the rat, rabbit, chicken and frog. 2. In all species the uptake of both hormones reaches a steady state at which the uptake of tri‐iodothyronine is 2‐4 times that of thyroxine. 3. The uptake of thyroid hormones by perfused hearts can be resolved into two distinct components—first, an initial transient process which takes up hormone and then releases it with a peak uptake at about 20 min from the beginning of perfusion and second, a basic, slow‐uptake process which takes several hours to reach a steady state and which has a greater affinity for tri‐iodothyronine. Analysis of the ‘initial uptake‐and‐release effect’ suggests that it is due to the presence of plasma thyroxine‐binding protein in the interstitial fluid of the heart. 4. These two uptake processes provide the basis for the biphasic release of thyroid hormones previously described for the rat heart.