Sarcoplasmic reticulum Ca(2+)ATPase and cell contraction in developing rabbit heart.

Area of Science:

• Cardiovascular Physiology
• Molecular Cardiology
• Cell Biology

Background:

• Cardiac function matures postnatally.
• Sarcoplasmic reticulum Ca(2+)-ATPase (SERCA2a) is crucial for cardiac muscle relaxation.
• Age-related changes in SERCA2a may impact cardiac contractility.

Purpose of the Study:

• To investigate age-related changes in cardiac SERCA2a expression and function.
• To determine if SERCA2a immaturity contributes to reduced SR Ca(2+) release in immature hearts.

Main Methods:

• Quantitative analysis of SERCA2a protein levels and localization in rabbit hearts at different developmental stages (fetal, neonatal, juvenile, adult).
• In situ functional assessment of SERCA in isolated cardiac myocytes by measuring SR Ca(2+) store reloading rates after caffeine-induced depletion.

Main Results:

• Significant SERCA2a expression is present early in immature hearts, reaching adult levels within 15-30 days post-birth.
• SERCA2a protein exhibits transverse striations within myocytes from 1 day of age.
• In situ SERCA function in neonatal and adult myocytes is comparable in maintaining SR Ca(2+) stores.

Conclusions:

• Immature cardiac myocytes do not exhibit a paucity of SERCA2a expression.
• The reduced SR Ca(2+) release observed in immature ventricular myocytes is not attributable to SERCA2a immaturity.