Chronic stimulation-induced changes in mitochondria and performance in rat skeletal muscle

Abstract

Chronic low-frequency (10-Hz) electrical stimulation was used to investigate mitochondrial biogenesis in rat tibialis anterior muscle. Succinate dehydrogenase and citrate synthase were used as mitochondrial enzymes, and cardiolipin (CL) was used as a phospholipid index of the inner membrane. Stimulation was via the peroneal nerve (24 h/day) for 1, 2, 3, 5, 7, 10, 14, 21, and 28 days (n = 3-9 rats/day). After each period, endurance performance was evaluated in situ. The contralateral side (CON) served as control nonstimulated muscle. Endurance performance gradually improved after 5 days of stimulation to approximately twofold higher than CON muscle beyond 10 days. Succinate dehydrogenase activity rose to 2.4-fold above CON muscle (4.8 +/- 0.2 U/g; n = 54) by 10 days (half time = 6.1 days) and then remained constant. Citrate synthase demonstrated a similar change. The improved performance with stimulation was correlated (r = 0.61, P < 0.05) to these increases in enzyme activities. CL concentration increased from CON (0.35 +/- 0.02 mumol/g; n = 30) to 3.6- and 3.8-fold above CON at 10 and 14 days (half time = 4.2 days). This increase in CL was greater (P < 0.05) than for either enzyme during the same period. These data are consistent with a model of mitochondrial membrane biogenesis in which enzyme proteins are inserted into a presynthesized lipid bilayer.

Effect of prior chronic contractile activity on mitochondrial function and apoptotic protein expression in denervated muscle

“…It has been well established that skeletal muscle mitochondrial content is particularly sensitive to changes in contractile activity (1,3,7,14,26,27). In the present study, we show that chronic stimulation results in an increase in whole muscle mitochondrial content (Fig.…”

“…Constant, Quebec, Canada) were given food and water ad libitum. The implantation of electrodes and the chronic stimulation procedures were performed as previously described (26) and were approved in accordance with the regulations of the York University Animal Care Committee. Briefly, rats were anesthetized with an intraperitoneal injection of xylazineketamine (0.2 ml/g body wt).…”

Protein Import into Subsarcolemmal and Intermyofibrillar Skeletal Muscle Mitochondria

“…Our data indicate a greater reliance of SS mitochondria on acidic phospholipids such as cardiolipin for import; they establish the importance of precursor-phospholipid interactions for protein import in subtypes of mammalian mitochondria; and they represent another indication that the regulation of import in these two mitochondrial subfractions differs. These data also have implications for mitochondrial biogenesis, since we have previously shown that large and rapid increases in cardiolipin content occur in muscle responding to chronic contractile activity prior to substantial increases in mitochondrial enzyme activity (36). Thus, an initial increase in cardiolipin content within the organelle could facilitate the subsequent import of proteins, particularly in SS mitochondria.…”

Kinase-specific responsiveness to incremental contractile activity in skeletal muscle with low and high mitochondrial content

“…All experiments involving animals were evaluated and approved by the York University Animal Care Committee in accordance with the regulations of the Canadian Council on Animal Care. Animals were prepared essentially as described previously (73). They were anesthetized with pentobarbital sodium (60 mg/kg), and the left common carotid artery was catheterized (PE-50) to allow us to monitor hemodynamic parameters with the use of a pressure transducer (model RS 3200, Gould, Cleveland, OH).…”