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Postnatal development of palmitate oxidation and mitochondrial enzyme activities in rat cardiac and skeletal muscle
Insights
Palmitate oxidation in developing rat muscles shows a rapid postnatal surge in the diaphragm and flexor digitorum brevis, followed by a decline. Cardiac and skeletal muscle oxidative capacity increases with development, driven by mitochondrial adaptations.
Area of Science:
- Biochemistry
- Developmental Biology
- Exercise Physiology
Background:
- Muscle development involves significant metabolic shifts.
- Fatty acid oxidation is crucial for energy production in various tissues.
- Understanding developmental changes in muscle metabolism is key to comprehending physiological maturation.
Purpose of the Study:
- To investigate the developmental changes in palmitate oxidation rates in rat skeletal and cardiac muscles.
- To examine the activity of key mitochondrial enzymes during muscle development.
- To elucidate the mechanisms underlying the maturation of oxidative capacity in different muscle types.
Main Methods:
- Measurement of palmitate oxidation rates in intact and homogenized rat muscles (heart, diaphragm, m. flexor digitorum brevis, m. quadriceps) from late fetal life to maturity.
- Assay of mitochondrial enzyme activities (cytochrome c oxidase, citrate synthase).
Main Results:
- Palmitate oxidation rate increased significantly immediately after birth in diaphragm and m. flexor digitorum brevis, then decreased to adult levels (~35% of birth values).
- Oxidative capacities of heart, diaphragm, and m. quadriceps steadily increased during development, reaching adult levels by 15-20 days postnatally.
- Mitochondrial enzyme activities mirrored the developmental pattern of oxidative capacity.
- In heart, increased oxidative capacity resulted from higher mitochondrial content and activity; in diaphragm and m. quadriceps, it was due to increased mitochondrial activity despite decreased mitochondrial content.
Conclusions:
- Muscle oxidative capacity undergoes significant developmental regulation.
- Distinct mechanisms govern the maturation of oxidative function in cardiac versus skeletal muscles.
- Mitochondrial biogenesis and functional adaptation are critical for achieving mature muscle energy metabolism.
Abstract:
1. The palmitate oxidation rate was measured in intact diaphragm and m. flexor digitorum brevis and in whole homogenates of heart, diaphragm and m. quadriceps of developing rats between late foetal life and maturity. Activities of the mitochondrial enzymes cytochrome c oxidase and citrate synthase were also determined. 2. Immediately after birth the palmitate oxidation rate increases markedly in both intact diaphragm and m. flexor digitorum brevis and falls gradually after day 1 to adult values which are about 35% of those at birth. 3. The oxidation capacities of diaphragm and m. quadriceps, but especially of heart, increase steadily during development, starting before birth and reaching adult values at 15-20 days postnatally. The activities of the mitochondrial enzymes show a similar developmental pattern. 4. In heart the increase of oxidative capacity is the result of an increase of both mitochondrial content and mitochondrial activity. The mitochondrial contents of diaphragm and m. quadriceps, on the other hand, decrease with age and the increase of their oxidative capacities is due to a large rise of the mitochondrial activity.