Related Experiment Videos
Structure of tight junctions in epithelia with different permeability
Summary
Epithelial tight junction permeability is not solely determined by fibril network complexity. Unseen junctional features play a key role in regulating epithelial barrier function.
Area of Science:
- Cell Biology
- Epithelial Physiology
- Membrane Biology
Background:
- Freeze-fracture studies reveal intramembrane fibrils in epithelial tight junctions.
- Previous research suggested a direct correlation between fibril number and junctional permeability.
Purpose of the Study:
- To investigate the relationship between tight junction structure and epithelial permeability.
- To determine if fibril network complexity solely dictates junctional permeability.
Main Methods:
- Utilized freeze-fracture electron microscopy to examine tight junction structure.
- Assessed epithelial permeability using lanthanum as a tracer in rabbit ileum and toad urinary bladder.
- Manipulated toad urinary bladder permeability by creating hypertonic luminal solutions with lysine.
Main Results:
- Rabbit ileum tight junctions, despite complex fibrils, were permeable to lanthanum.
- Toad urinary bladder tight junctions, normally impermeable, became permeable to lanthanum under hypertonic lysine conditions.
- Freeze-fracture analysis showed no structural differences in fibrils between control and lysine-treated toad bladders.
Conclusions:
- Epithelial junctional permeability is not exclusively determined by the complexity of the fibril network visible in freeze-fracture images.
- Factors beyond the observable fibril network, potentially unvisualized features of the junctions or fibrils, are critical regulators of epithelial permeability.