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Species differences in cardiac thyroid hormone receptor isoforms protein abundance
1Karolinska Institute, Department of Cardiology, Huddinge University Hospital, Stockholm, Sweden.
Biological & Pharmaceutical Bulletin
|December 24, 1997
Summary
Thyroid hormone receptor (TR) isoform expression varies by species and tissue. This study identified unique TR isoform distributions in human and animal hearts, revealing TR beta 2 in humans for the first time.
Area of Science:
- Endocrinology
- Molecular Biology
- Cardiology
Background:
- Thyroid hormone receptors (TRs) regulate gene expression, but their specific roles in cardiac tissue are not fully understood.
- Knowledge of TR isoform expression patterns is crucial for understanding thyroid hormone action in the heart.
Purpose of the Study:
- To investigate the protein-level expression of different thyroid hormone receptor (TR) isoforms in the heart across various species and in human tissues.
- To characterize the distribution of TR isoforms in cardiac and non-cardiac tissues.
Main Methods:
- Western blot analysis was employed using specific antibodies against TR isoforms.
- Samples analyzed included left ventricle myocardium from humans, dogs, guinea pigs, rats, and mice.
- Human tissues examined were heart, skeletal muscle, brain, liver, and thyroid.
Main Results:
- TR alpha 1 was ubiquitously expressed across all species and in human heart and skeletal muscle.
- TR alpha 2 was detected in human, dog, and guinea pig hearts but not in rat or mouse hearts.
- TR beta 1 was absent in human heart but present in other species' hearts. TR beta 2 was found in all species' hearts and all examined human tissues, including the first demonstration in humans.
- TR alpha 2 was exclusively found in the human heart among the tested human tissues.
Conclusions:
- Thyroid hormone receptor (TR) isoform expression exhibits significant tissue and species-specific patterns.
- The unique distribution of TR isoforms suggests distinct roles in regulating gene expression within different tissues and species.
- The identification of TR beta 2 in human tissues provides new insights into thyroid hormone signaling and its potential impact on variable tissue effects.