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Human thyroxine‐binding globulin and thyroxine‐binding pre‐albumin: dissociation rates
Author(s) -
Hillier A. P.,
Balfour W. E.
Publication year - 1971
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.1971.sp009589
Subject(s) - thyroxine binding globulin , globulin , chemistry , endocrinology , albumin , dissociation (chemistry) , thyroxine binding proteins , medicine , plasma protein binding , biochemistry , thyroid , thyroid function tests , thyroid hormones
1. A simple method is described for estimating the rate of thyroxine dissociation from binding sites in plasma. 2. At tracer concentrations in human plasma thyroxine dissociates at two distinct exponential rates. These are due to the two thyroxine‐binding proteins present in human plasma. 3. The t ½ for thyroxine dissociation from thyroxine‐binding globulin is 8·1 ± 0·7 ( S.E. ) min at room temperature and 38·6 ± 2·1 sec at 37° C. 4. The t ½ for thyroxine dissociation from thyroxine‐binding pre‐albumin is 53 ± 5·0 sec at room temperature and 7·9 ± 0·3 sec at 37° C. 5. Dissociation of thyroxine from both proteins is a single exponential process, suggesting that each protein has only one type of specific binding site. 6. These results indicate that the minute pool of free thyroxine in plasma is turning over about 100 times each second, with about two thirds of this flux being due to release and binding of the hormone by pre‐albumin.