Key Points
- Investigate the regulation of cardiac troponin I and slow-skeletal troponin I mRNA expression during development and in response to altered thyroid hormone status in rat hearts.
- Measured cardiac troponin I (cTnI) and slow-skeletal troponin I (ssTnI) mRNA levels using Northern blots and RNA slot blots across perinatal and adult rats.
- Assessed and compared euthyroid, hypothyroid, and triiodothyronine (T3)-treated hypothyroid rat ventricular tissue preparations at various postnatal stages (day 3 to day 125).
- Euthyroid hearts displayed a 6-fold increase in cTnI mRNA from day 3 to day 21 compared to a 3-fold increase in hypothyroid hearts, while ssTnI mRNA clearance was delayed in hypothyroid hearts (disappearing after 21 days vs. 14 days in euthyroid).
- Significant differences in cTnI mRNA levels occurred between euthyroid and T3-treated hypothyroid preparations at 28 days, and between euthyroid and hypothyroid ventricles at 87 to 125 days.
- T3 administration in 87- to 125-day-old hypothyroid rats did not elevate cTnI mRNA above euthyroid levels despite high serum T3 concentrations.
Structured PICO
PPopulationPerinatal and young adult rat hearts (ages 3 to 125 days)
IInterventionHypothyroidism and T3 treatment
OOutcomemRNA levels for cardiac troponin I (cTnI) and slow-skeletal troponin I (ssTnI)surrogate
Thyroid hormone regulates the developmental switching of troponin I isoforms in the rat heart, with its influence diminishing in older animals.