Age effects on cytochrome oxidase activities during denervation and recovery of three muscle fiber types

Abstract

The rat nasolabialis muscle is comprised of a mosaic of red, white, and intermediate muscle fiber types. Using computerized microdensitometry, cytochrome oxidase (COX) activity was quantitatively analyzed in each fiber type throughout the period of denervation and recovery in young adult (3-month) and middle-aged (15-month) male Sprague-Dawley rats. In animals of both age groups, the nasolabialis muscle on one side of the head was denervated by crushing the facial nerve. At specific days post crush (dpc) ranging from 2 days-2 months, animals were sacrificed and thick sections of normal and denervated muscles were incubated to demonstrate the activity of COX, a mitochondrial enzyme, which differentiates between the three fiber types. Enzyme activities in individual fibers were microdensitometrically analyzed using a digitizing image analyzer. Although a denervation-induced decreased followed by eventual recovery occurred in all fibers of each type, age-related differences were evident. For all types, younger fibers consistently showed decreased COX activity sooner than their older counterparts, and older fibers of all types consistently showed a greater decreased COX activity than the younger fibers. Denervation-induced de-differentiation of muscle fibers led to a more homogeneous population of fiber types in both age groups. Following recovery of function, the magnitude of the fiber enzyme activity change differed according to fiber type and to age, and was consistently smaller in older animals. The normal mosaic pattern of fiber type distribution and normal COX levels were restored 2 months after nerve lesion in both age groups.

Time course of changes in lipoprotein lipase activity in rat skeletal muscles during denervation-reinnervation

“…These changes lead to more glycolytic metabolism in red muscles. In the recovering muscle during reinnervation, the fiber types are transformed back into more oxidative, the activity of oxidative enzymes increases and the muscle shifts back to more oxidative metabolism (6,8,38).…”

“…skeletal muscle; denervation; reinnervation PERIPHERAL NERVE CRUSH leads to functional denervation of muscles with a variety of degenerative changes in muscle morphology and biochemistry that subsist until the regeneration of injured nerve takes place. The changes include an immediate loss of muscle activity followed by atrophy and degeneration of muscle fibers, a decrease in mitochondrial oxidative enzyme activities, and a fall in high-energy phosphate contents (6,8,21,38). Reinnervation and regeneration of skeletal muscles result in restoration, to some degree, of the original muscle fiber structure and contractile activity accompanied by a reversal of some previous biochemical alterations (8,12,24,25).…”

“…ations induced by denervation is different for enzymes of various metabolic pathways, and so it depends on the muscle fiber type (33,38).…”

The expression patterns of β1,4 galactosyltransferase I and V mRNAs, and Galβ1-4GlcNAc group in rat gastrocnemius muscles post sciatic nerve injury

“…Scale bars=20 μm after SD rat sciatic nerve injury. Previous researches have shown that pathological changes in peripheral nerve system including damages, inflammation, tumor and denaturation could result in acute, subacute or chronic denervation, which is in turn responsible for the atrophy of target muscles [5,34]. But the molecular mechanisms of muscular atrophy, due to denervation remain to be elucidated.…”

Age-related structural and compositional variations of mouse skeletal muscle

“…However, many studies only accessed 2 age groups, i.e. young and adult or young and old animals, to investigate the age-related variations [38,78,79]. The alterations that occur in skeletal muscle during different stages of aging, i.e.…”