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Carrier-mediated [125I]-T3 uptake by mouse thymocytes
M Centanni1, G Mancini, M Andreoli
1Department of Experimental Medicine, University La Sapienza, Rome, Italy.
Endocrinology
|May 1, 1989
Summary
Thyroid hormone (T3) enters thymocytes via a specific, energy-dependent process. This uptake is saturable and influenced by temperature and ion transport, suggesting active cellular mechanisms for thyroid hormone regulation.
Area of Science:
- Endocrinology
- Cell Biology
- Molecular Biology
Background:
- Thymocytes are key targets of thyroid hormones.
- Understanding thyroid hormone transport into cells is crucial for comprehending their biological effects.
Purpose of the Study:
- To investigate the mechanism of thyroid hormone (T3) entry into thymocytes.
- To characterize the kinetics and cellular requirements of T3 uptake.
Main Methods:
- Incubation of thymocytes with radiolabeled L-T3 ([125I]L-T3).
- Kinetic analysis of uptake rates and saturation.
- Washout experiments at different temperatures.
- Assessment of energy dependence (oligomycin) and cation involvement (ouabain).
Main Results:
- T3 uptake was linear up to 2 minutes, then plateaued, indicating a saturable process.
- Specific T3 uptake represented 48% of total uptake at equilibrium.
- Uptake showed stereospecificity for L-T3 and was energy-dependent (sensitive to oligomycin) and involved cation transport (sensitive to ouabain).
- Temperature significantly affected uptake and hormone retention, with lower temperatures reducing uptake and increasing release.
Conclusions:
- Thymocytes possess a stereospecific, energy-dependent, and saturable transport system for T3 entry.
- This process is influenced by cellular energy status and cation gradients.
- The findings highlight active mechanisms regulating intracellular thyroid hormone levels in thymocytes.