Dexamethasone treatment improves sarcoplasmic reticulum function and contractile performance in aged myocardium

Area of Science:

• Cardiovascular Physiology
• Molecular Cardiology
• Gerontology

Background:

• Corticosteroids play a role in myocardial function, but mechanisms are not fully understood.
• Aging impairs cardiac contractile performance and sarcoplasmic reticulum (SR) calcium (Ca2+) handling.
• Glucocorticoids may offer therapeutic potential for age-related cardiac dysfunction.

Purpose of the Study:

• To investigate the therapeutic potential of dexamethasone in reversing age-associated cardiac dysfunction.
• To assess the impact of dexamethasone on myocardial contractile performance in senescent rats.
• To determine if dexamethasone improves SR Ca2+ sequestration function in aged hearts.

Main Methods:

• Senescent male Fischer 344 rats (26-28 months old) received dexamethasone (4 microg/h for 5 days) or vehicle via osmotic mini pumps.
• Cardiac contractile performance was evaluated in Langendorff-perfused, electrically paced hearts.
• ATP-energized Ca2+ uptake rates were measured in isolated SR vesicles.

Main Results:

• Dexamethasone treatment significantly improved myocardial contractile performance in aged rats.
• Developed peak tension increased by 30-60% across various beating frequencies (2-6 Hz).
• Time to half-relaxation decreased by 8-15%, and SR Ca2+ uptake doubled compared to controls.

Conclusions:

• Glucocorticoid treatment with dexamethasone can reverse age-related deficits in cardiac contractile force and duration.
• Dexamethasone enhances SR Ca2+ pump function, improving calcium sequestration in senescent hearts.
• These findings highlight a potential therapeutic strategy for age-associated heart dysfunction via glucocorticoid-mediated SR improvements.