The specific binding of the thyroid hormones to matrix isolated from rat liver nuclei
The original publication is available at http://www.samj.org.za
Specific binding sites for the thyroid hormones have been demonstrated in the liver nuclear matrix, a structural framework of the nucleus. When labelled 3,5,3'-tri-iodo-L-thyronine ([125I]T3) is injected into rats, 5% of the total nucleus bound T3 is bound to the matrix after 1 hour. However, when either isolated nuclei or isolated nuclear matrices were incubated with [125I]T3 in vitro, a 3- to 7-fold greater number of specific T3 binding sites were revealed in the nuclear matrix. The proporties of the matrix-associated thyroid hormone binding sites were investigated in vitro. These binding sites showed limited capacity and high affinity for T3; the equilibrium association constant (K(a)) was 1.3 x 109 M-1 and the binding capacity was 20.2 fmol T3 per 100 μg matrix protein.
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