Related Experiment Videos
Functional development of the creatine kinase system in perinatal rabbit heart
J A Hoerter1, A Kuznetsov, R Ventura-Clapier
1Laboratoire de Physiologie Cellulaire Cardiaque, INSERM U-241, Université Paris-Sud, Orsay, France.
Insights
The creatine kinase system
Area of Science:
- Cardiovascular Physiology
- Biochemistry
- Developmental Biology
Background:
- The creatine kinase system is crucial for cellular energy buffering in the heart.
- Understanding its developmental trajectory is key to comprehending cardiac maturation.
- Isoforms of creatine kinase (CK) play distinct roles in energy metabolism.
Purpose of the Study:
- To investigate the functional development of the creatine kinase (CK) system in rabbit hearts during perinatal growth.
- To characterize the developmental changes in myofibrillar and mitochondrial CK activities.
- To elucidate the role of CK compartmentation in postnatal cardiac cellular maturation.
Main Methods:
- Rabbit hearts were analyzed at various developmental stages (fetal, neonatal, adult).
- Enzyme activity assays were performed on Triton X-100-skinned and saponin-skinned cardiac fibers.
- Functional assessments included measuring ATP-independent tension development and creatine-stimulated respiration.
Main Results:
- Total CK activity remained constant, but myofibrillar CK activity increased 15-fold in the first postnatal week.
- Functional activity of myofibrillar CK was low at birth, increasing to adult levels by 17 days.
- Mitochondrial CK functional activity emerged postnatally and gradually increased over the first 17 days.
- Both mitochondrial and myofibrillar CK functional activities developed in parallel, despite different expression stages.
Conclusions:
- Postnatal cardiac development involves the parallel functional maturation of mitochondrial and myofibrillar creatine kinase.
- Early postnatal development is marked by the binding of CK isoenzymes to intracellular organelles.
- This compartmentation of creatine kinase is integral to postnatal cardiac cellular maturation and energy buffering.
Abstract:
The functional development of the creatine kinase system has been studied in rabbit heart during perinatal growth. Fiber bundles were obtained from left ventricles of fetal rabbits at the 30th day of gestation, newborn rabbits aged 1, 3, 8, and 17 days, and adult rabbits. Total creatine kinase activity was constant during perinatal development, whereas myofibrillar bound creatine kinase activity increased 15-fold during the first postnatal week. Functional activity of myofibrillar creatine kinase was assayed in Triton X-100-skinned fibers by its ability to induce active tension in the absence of ATP or to relax rigor tension. It was very low in 1-day-old newborns and increased during the first 2 weeks to reach adult levels 17 days after birth. Functional activity of mitochondrial creatine kinase was determined in saponin-skinned fibers. Creatine-stimulated respiration appeared only after birth and increased gradually between 1 and 17 days after birth. The results show that, although the two creatine kinase isoforms (mitochondrial and myofibrillar) are expressed at different stages during development, their functional activities appear in parallel in mitochondria and myofibrils. Early postnatal development is characterized by binding of creatine kinase isoenzymes to intracellular organelles. Such compartmentation participates in the postnatal cardiac cellular maturation.