Related Experiment Videos
Immunoreactive and bioactive isoforms of human thyrotropin.
I Sergi1, M J Papandreou, G Medri
1Laboratoire de Biochimie, URA 1179 CNRS, Marseille, France.
Endocrinology
|June 1, 1991
Summary
Thyroid-stimulating hormone (TSH) isoforms exhibit distinct immunoreactive and bioactive properties. These TSH variations influence their potency in stimulating thyroid cells, challenging the direct correlation between immunoreactivity and biopotency.
Area of Science:
- Endocrinology
- Molecular Biology
- Biochemistry
Background:
- Thyroid-stimulating hormone (TSH) is crucial for thyroid function.
- TSH exists in various isoforms with potentially different biological activities.
- Understanding TSH isoform heterogeneity is key to interpreting thyroid function tests.
Purpose of the Study:
- To characterize the heterogeneity of human intrapituitary TSH isoforms.
- To analyze the immunoreactivity and bioactivity of distinct TSH isoforms.
- To investigate the relationship between TSH isoform structure and function.
Main Methods:
- Isoelectric focusing of intrapituitary human TSH.
- Immunoblotting using polyclonal and monoclonal antibodies against TSH subunits and epitopes.
- Assessment of cAMP production and FRTL-5 rat thyroid cell growth stimulation.
Main Results:
- Seven major TSH isoforms (pI 6.0-8.6) were identified, distinct from alpha and beta subunit patterns.
- Polyclonal and monoclonal antibodies showed differential binding to neutral/alkaline versus acidic TSH isoforms.
- All TSH isoforms induced cAMP and cell growth, but neutral forms were less potent.
- The bioactive/immunoreactive ratio varied among isoforms, indicating distinct functional domains.
Conclusions:
- Human TSH isoforms exhibit significant structural and functional heterogeneity.
- Immunoreactivity and bioactivity of TSH isoforms are differentially regulated.
- The bioactive/immunoreactive ratio is not a reliable indicator of TSH biopotency.