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Thyroid epithelial morphogenesis in vitro: a role for bumetanide-sensitive Cl- secretion during follicular lumen
A S Yap1, B R Stevenson, J W Armstrong
1Department of Physiology and Pharmacology, University of Queensland, St. Lucia, Brisbane, Australia.
Experimental Cell Research
|August 1, 1994
Summary
Thyroid follicular development involves two phases: initial lumen formation and subsequent growth. Bumetanide inhibits lumenal growth by blocking chloride transport, crucial for follicular development.
Area of Science:
- Cell Biology
- Endocrinology
- Epithelial Physiology
Background:
- Thyroid follicles are the structural and functional units of the thyroid gland, comprising a lumen enclosed by polarized epithelial cells.
- Understanding the mechanisms of follicular lumen development is crucial for comprehending thyroid gland formation and function.
Purpose of the Study:
- To characterize the process of lumenal development during the reorganization of primary porcine thyroid cells into follicles.
- To investigate the role of NaK2Cl cotransport in thyroid follicular lumen formation and growth.
Main Methods:
- Primary cultures of porcine thyroid cells were used to study follicular reorganization.
- Laser scanning confocal microscopy and immunohistochemistry were employed to visualize cell structures and protein localization.
- Electrophysiological studies were conducted to assess ion transport and its contribution to the electrical potential difference.
Main Results:
- Bumetanide, a NaK2Cl cotransport inhibitor, inhibited normal follicle formation and subsequent lumenal growth, despite allowing cell polarization and tight junction assembly.
- Electrophysiological studies confirmed that bumetanide-sensitive chloride transport significantly contributed to the transepithelial electrical potential difference.
- Bumetanide did not affect cell proliferation, and thyroglobulin was not detected in the lumena of cultured follicles.
Conclusions:
- Thyroid follicular reorganization involves two distinct phases: initial lumen formation (apical membrane domain assembly) and subsequent lumenal growth.
- Inward chloride transport by polarized epithelial cells, mediated by NaK2Cl cotransport, is essential for sustained follicular lumenal growth.
- These findings elucidate key molecular mechanisms driving thyroid follicle development and lumen expansion.