Postnatal growth and differentiation in three hindlimb muscles of the rat

Abstract

The postnatal development, between 0 and 90 days, of three hindlimb muscles and diaphragm of the rat was investigated with respect to fiber types and diameter (histochemistry) and substrate oxidation rates and enzyme activities (biochemistry). The process of muscle fiber differentiation into mature patterns was evaluated by visual classification into 3 or 4 groups having different staining intensities for 3 enzyme-histochemical reactions, enabling 26 fiber types to be distinguished. These exhibited specific sizes and growth rates that varied among the muscles. One of the hindleg muscles (flexor digitorum brevis) remained much more immature than soleus and extensor digitorum longus. The histochemical and biochemical findings correlated well. The capacity for pyruvate and palmitate oxidation, and the activities of cytochrome c oxidase and citrate synthase, increased markedly between 9 and 37 days in soleus and extensor digitorum longus (except citrate synthase in the latter) but not in flexor digitorum brevis. Creatine kinase activity increased in all hindlimb muscles. Both the capacity and the activity of pyruvate oxidation (determined in homogenates and intact isolated muscles, respectively), were in accordance with the fiber type composition. In contrast to oxidation capacity, the activity of pyruvate oxidation decreased after birth until the mature stage, when a value of 18-42% of that of early postnatal muscles was recorded.

Differences in ultrastructural and metabolic profiles within the same type of fibres in various muscles of young and adult rats

“…It was found that there were differences between V,, and SDH activity in all types of fibre in different muscles in each age group as reported by Goldspink (1969) and Zuurveld et al (1985). However, the authors also found different patterns in different fibre types.…”

Human tissue-engineered skeletal muscle: a novel 3D in vitro model for drug disposition and toxicity after intramuscular injection

“…Also significant higher CK content was observed in BAM-MM. Creatin kinase expression is highly increased during myogenesis and reflects the maturity grade of myofibers 54 , 55 . From the above, we can conclude that both BAM-M and BAM-MM have clear myogenic features but are less mature than adult muscle and that BAM-MM shows more pronounced differentiation than BAM-M.…”