[Bioenergetic characteristics of the diaphragm after spinal cord injury].
BACKGROUND
C2 spinal cord hemisection interrupts descending bulbospinal respiratory axons coursing through the cervical spinal cord. One consequence of this type of spinal cord injury is the partial deafferentation of the ipsilateral phrenic nucleus, which renders the hemidiaphragm paralysed. The biochemical properties of the intact or denervated locomotor skeletal muscles have been studied extensively, whereas the biochemical properties of the diaphragm after a cervical spinal cord injury received relatively little attention. This seems unfortunate, given that the diaphragm is the most important mammalian respiratory muscle and is the only skeletal muscle considered essential for survival. Therefore, the purpose of this work was to analyse the bioenergetic characteristics of the diaphragm following a cervical spinal cord injury.


METHODS
Segments of the crural diaphragm from rat were homogenised to determine the activities of a glycolytic enzyme, lactate dehydrogenase (LDH), and a Krebs cycle enzyme, citrate synthase (CS).


RESULTS
Data show a significant decrease of the CS activity on the ipsilateral hemidiaphragm to the cervical hemisection. No change in the LDH is observed between the animal without or with a cervical spinal cord injury.


CONCLUSIONS
These data suggested that the CS activity could be dependent of the nervous influx from the central respiratory rhythm generator and that LDH activity could be maintained by a peripheral respiratory activity or by the cross phrenic phenomenon activation. Biochemical data should be considered in subjects presenting respiratory deficiency induced by a cervical spinal cord injury. Furthermore, the diaphragmatic muscle metabolic activity could be used to evaluate the functional respiratory recovery observed spontaneously or experimentally after using repair strategies of the spinal cord.
Marqueste
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Laboratoire de Physiopathologie Respiratoire Cellulaire et Intégrée (UPRES EA 2201), Institut Fédératif de Recherches Jean Roche (IFR11), Faculté de Médecine Nord, Université de la Méditerranée (Aix-Marseille II), Marseille, France.
Decherchi
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D000818:Animals; D003964:Diaphragm / Q000378:metabolism*; D004734:Energy Metabolism; D005260:Female; D051381:Rats; D017207:Rats, Sprague-Dawley; D013119:Spinal Cord Injuries / Q000378:metabolism*