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Phosphorylcreatine shuttle enzymes during perinatal heart development
Insights
During mammalian heart development, the phosphorylcreatine shuttle system significantly enhances cardiac function. Key enzymes like creatine kinase show substantial increases, contributing to improved heart performance from weaning to adulthood.
Area of Science:
- Cardiovascular Physiology
- Biochemistry
- Developmental Biology
Background:
- Mammalian heart function significantly improves from weaning to adulthood.
- This enhancement correlates with increased aerobic metabolism and contractile protein ATPase activity.
Purpose of the Study:
- To investigate the role of phosphorylcreatine shuttle enzymes in developmental changes in heart performance.
- To understand the enzymatic basis for enhanced cardiac function during postnatal development.
Main Methods:
- Assessed mitochondrial and myofibrillar ATPase specific activity in weanling and adult hearts.
- Measured creatine kinase activity in both mitochondrial and myofibrillar fractions.
- Evaluated changes in calcium sensitivity and purified myosin ATPase activity.
Main Results:
- Mitochondrial ATPase activity remained unchanged, but creatine kinase activity increased threefold.
- Myofibrillar ATPase activity doubled, with a proportionally greater increase in myofibrillar creatine kinase activity.
- Enhanced myofibrillar ATPase activity was not linked to calcium sensitivity or purified myosin alterations.
Conclusions:
- Enzymatic reactions of the phosphorylcreatine shuttle system are significantly upregulated during normal heart development.
- The enhanced phosphorylcreatine shuttle system is a key contributor to improved cardiac function in the perinatal period.
- This mechanism is crucial for supporting the energetic demands of the growing mammalian heart.
Abstract:
Mammalian heart development, from the time of weaning until adulthood, is characterized by progressive and significant enhancement in functional performance. Aerobic metabolism and contractile protein ATPase activity increase in parallel with augmented cardiac function. The present studies examined the potential contribution of phosphorylcreatine shuttle enzymes to the developmentally linked alterations in heart performance. Mitochondrial ATPase specific activity was not altered between weanling and adult heart; however, creatine kinase activity was enhanced approximately threefold. Myofibrillar ATPase activity doubled over the developmental time course, while creatine kinase activity increased to an even greater extent. Enhanced myofibrillar ATPase activity was not due to alterations in either calcium sensitivity or ATPase activity measured in purified myosin. Both the mitochondrial and myofibrillar creatine kinase enzyme activities are enhanced during normal heart growth; however, relatively greater enhancement of the myofibrillar component occurs. Thus, enzymatic reactions comprising the phosphorylcreatine shuttle system are dramatically increased during normal heart development. This mechanism deserves consideration as a potentially powerful contributor to enhanced cardiac function during the perinatal period.