Human Thyroid Membranes Research Articles

The relation between lipid mobility and the specific hormone binding of thyroid membranes

1. The specific binding of thyroid-stimulating hormone to isolated human thyroid membranes was examined under a variety of conditions. 2. In phosphate-saline buffer (in the presence of 0.14 M-NaCl) on increasing the temperature the binding of the hormone is increased, the plots of bound/free hormone against temperature showing a distinct break around 30 degrees C. 3. Detailed analysis showed that the increased binding is associated with an increase in the number of binding sites. 4. The motional characteristics of three membrane-bound fluorescent probes, 2-(9-anthroyl)palmitic acid, 12-(9-anthryl)stearic acid and N-1-naphthyl-N-phenylamine, were also examined as a function of temperature by measuring both fluorescence polarizations and lifetimes. 5. The results indicated that the 'fluidity' of membrane lipids also increased with temperature. The temperature-dependence of this property also shows a change at about 30 degrees C. 6. Bivalent cations decreased both membrane fluidity and hormone binding. 7. Similar correlations were found between the binding of adrenocorticotrophic hormone and the fluidity of the plasma membranes obtained from adrenal-cortical cells, with the discontinuity occurring in this case at 23 degrees C. 8. The possibility of lipid mobility being important in controlling hormone-receptor function is discussed.

A radio-ligand receptor assay for the long-acting thyroid stimulator. Inhibition by the long-acting thyroid stimulator of the binding of radioiodinated thyroid-stimulating hormone to human thyroid membranes.

Highly purified bovine TSH (thyroid-stimulating hormone) was labelled with 125I by using very low concentrations of chloramine-T. Human thyroid membranes prepared by discontinuous sucrose-density-gradient centrifugation were homogeneous on examination by electron microscopy. Incubation of radioiodinated TSH with the membranes showed that radioactivity could be bound to the membranes. Under the experimental conditions described here, binding was dependent on time and temperature and was a saturable phenomenon. Preincubation of the membranes with unlabelled hormone inhibited the subsequent binding of 125I-labelled TSH. Similarly, inhibition by the long-acting thyroid stimulator also showed a saturation behaviour. A rapid and sensitive method for the detection of the long-acting thyroid stimulator is described.

THYROID-STIMULATING IMMUNOGLOBULINS IN GRAVES' DISEASE

A receptor assay for T.S.H. using human thyroid membranes and receptor-purified 125I-labelled T.S.H. was used to study the interaction of Graves' immunoglobulins with thyroid membranes. Immunoglobulins from twenty-two of twenty-five patients with Graves' disease clearly inhibited the binding of T.S.H. to human thyroid membranes. Significant effects were also observed with one out of thirteen immunoglobulins from patients with Hashimoto's disease, and one out of six immunoglobulins from patients with thyroid cancer. Comparison of the effects of Graves' immunoglobulins on the binding of T.S.H. to human and guineapig thyroid membranes provided good evidence for the species specificity of some thyroid-stimulating immunoglobulins.

Binding of Thyroid Stimulators to Human Thyroid Membranes

Binding of Thyroid Stimulators to Human Thyroid Membranes