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TSH binding proteins in rat and human serum
Acta Endocrinologica
|August 1, 1987
Summary
Thyroid-stimulating hormone (TSH) in hypothyroid rats is primarily bound to serum proteins, retaining most of its biological activity. Exogenous TSH also binds to these proteins, suggesting potential autoimmune involvement.
Area of Science:
- Endocrinology
- Protein Chemistry
- Immunology
Background:
- Thyroid-stimulating hormone (TSH) plays a crucial role in thyroid function.
- The binding characteristics and biological activity of circulating TSH are not fully understood.
- Hypothyroidism can alter TSH levels and potentially its interactions with serum proteins.
Purpose of the Study:
- To investigate the binding of endogenous and exogenous TSH to serum proteins in rats and humans.
- To determine the biological activity of protein-bound TSH.
- To explore potential autoimmune mechanisms in TSH binding.
Main Methods:
- Fractionation of rat serum using Sephadex G-100 chromatography.
- Immunoelectrophoresis and autoradiography to identify TSH binding proteins.
- Radioimmunoassay (RIA) for immunoreactivity.
- In vitro bioassay measuring 99Tc uptake by FRTL-5 cells.
Main Results:
- Most endogenous immunoreactive TSH in hypothyroid rats circulates bound to high molecular weight proteins.
- Exogenous TSH binds to at least three serum protein fractions, including IgG and alpha-2-macroglobulin.
- The protein-bound TSH fraction contains the majority of the serum's immunoreactivity and bioactivity.
Conclusions:
- Endogenous TSH in hypothyroid rats is predominantly protein-bound and biologically active.
- TSH binding to serum proteins occurs in rats and humans, involving immunoglobulins.
- The presence of TSH-binding immunoglobulins suggests a possible role for autoimmune processes.