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Age-related changes in myocardial relaxation and sarcoplasmic reticulum function
T M Kaufman1, J W Horton, D J White
1Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas 75235.
The American Journal of Physiology
|August 1, 1990
Summary
Adult guinea pig hearts relax faster than newborn hearts when stimulated by isoproterenol. This difference is linked to the sarcoplasmic reticulum
Area of Science:
- Cardiovascular Physiology
- Developmental Biology
- Cellular Biology
Background:
- Rapid regulation of cardiac relaxation is crucial for adjusting stroke volume under stress.
- Calcium (Ca2+) transport by the sarcoplasmic reticulum (SR) significantly influences cardiac relaxation.
- Developmental changes in cardiac function are influenced by SR Ca2+ handling.
Purpose of the Study:
- To investigate developmental differences in isoproterenol's effect on cardiac relaxation time.
- To determine if age-related changes in SR Ca2+ transport correlate with these functional differences.
Main Methods:
- Isolated, perfused adult and newborn guinea pig hearts were used.
- Isovolumic relaxation time constant (tau) was measured.
- SR Ca2+ uptake, Ca2(+)-dependent ATPase activity, and Ca2+ pump density were assessed in isolated SR vesicles.
Main Results:
- Adult hearts exhibited a significantly greater decrease in tau with isoproterenol stimulation compared to newborn hearts.
- SR vesicles from adult hearts showed significantly higher Ca2+ uptake, Ca2(+)-dependent ATPase activity, and Ca2+ pump density than those from newborn hearts.
Conclusions:
- Developmental differences in the SR's Ca2+ sequestration capacity contribute to age-related variations in the heart's response to isoproterenol.
- Enhanced SR function in adult hearts facilitates more rapid relaxation.