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The uptake and release of thyroxine and tri‐iodothyronine by the perfused rat heart
Author(s) -
Hillier A. P.
Publication year - 1968
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.1968.sp008644
Subject(s) - perfusion , chemistry , medicine , endocrinology , triiodothyronine , bicarbonate , hormone , thyroid , reverse triiodothyronine , mammalian heart , biochemistry
1. The uptake and release of [ 131 I] L ‐thyroxine and L ‐3,5,3′‐tri‐iodothyronine have been studied in the rat heart perfused by Krebs—Ringer bicarbonate solution. 2. After 30 min perfusion thyroxine equilibrates to a ‘space’ of 15 ml./g of heart (i.e. each gram of tissue accumulates thyroxine equivalent to 15 ml. of perfusion fluid). Tri‐iodothyronine takes about 120 min to equilibrate to a ‘space’ of about 75 ml./g of heart. These results are independent of the concentration of the hormone between 1 × 10 −5 and 1·0 μg/ml. 3. The uptake of thyroxine at 17° C is almost identical with that at 37° C. 4. Radioactive thyroxine and tri‐iodothyronine are both released from the heart by two distinct exponential processes, viz. a rapid process with a half‐time of 14 min and a slow process with a half‐time of 60 min. About 30% of the total thyroxine and about 83% of the total tri‐iodothyronine are present in the slow‐release compartment.