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Na+,K+-ATPase concentration and fiber type distribution after spinal cord injury.
Muscle Nerve. 2004 Jan; 29(1):38-45.MN

Abstract

Complete spinal cord injury (SCI) is characterized, in part, by reduced fatigue-resistance of the paralyzed skeletal muscle during stimulated contractions, but the underlying mechanisms are not fully understood. The effects of complete SCI on skeletal muscle Na(+),K(+)-adenosine triphosphatase (ATPase) concentration, and fiber type distribution were therefore investigated. Six individuals (aged 32.0 +/- 5.3 years) with complete paraplegia (T4-T10; 1-19 years since injury) participated. There was a significantly lower Na(+),K(+)-ATPase concentration in the paralyzed vastus lateralis (VL) when compared to either the subjects' own unaffected deltoid or literature values (from our laboratory, utilizing the same methodology) of VL Na(+),K(+)-ATPase concentration for the healthy able-bodied (141.6 +/- 50.0, 213.4 +/- 23.9, 339 +/- 16 pmol/g wet wt., respectively; P < 0.05). There was also a significant negative correlation between the Na(+),K(+)-ATPase concentration in the paralyzed VL and years since injury (r = -0.75, P < 0.05). These findings are clinically relevant as they suggest that reductions in Na(+),K(+)-ATPase contribute to the fatigability of paralyzed muscle after SCI. Unexpectedly, the VL muscles of our subjects had a higher proportion of their area represented by type I fibers compared to literature values for the VL of the healthy able-bodied (52.6 +/- 25.3% vs. 36 +/- 11.3%, respectively; P < 0.05). As all our subjects had upper motor neuron injuries and, therefore, experienced muscle spasticity, our findings warrant further investigation into the relationship between muscle spasticity and fiber type expression after SCI.

Authors+Show Affiliations

Ditor DS
Department of Kinesiology, McMaster University, 1280 Main St. West, Hamilton, Ontario L8S 4K1, Canada.
Hamilton S
No affiliation info available
Tarnopolsky MA
No affiliation info available
Green HJ
No affiliation info available
Craven BC
No affiliation info available
Parise G
No affiliation info available
Hicks AL
No affiliation info available

MeSH

AdultDown-RegulationFemaleHumansMaleMuscle DenervationMuscle Fibers, Fast-TwitchMuscle Fibers, SkeletalMuscle WeaknessMuscle, SkeletalParaplegiaSodium-Potassium-Exchanging ATPaseSpinal Cord Injuries

Pub Type(s)

Comparative Study
Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

14694496

Citation

Ditor, D S., et al. "Na+,K+-ATPase Concentration and Fiber Type Distribution After Spinal Cord Injury." Muscle & Nerve, vol. 29, no. 1, 2004, pp. 38-45.
Ditor DS, Hamilton S, Tarnopolsky MA, et al. Na+,K+-ATPase concentration and fiber type distribution after spinal cord injury. Muscle Nerve. 2004;29(1):38-45.
Ditor, D. S., Hamilton, S., Tarnopolsky, M. A., Green, H. J., Craven, B. C., Parise, G., & Hicks, A. L. (2004). Na+,K+-ATPase concentration and fiber type distribution after spinal cord injury. Muscle & Nerve, 29(1), 38-45.
Ditor DS, et al. Na+,K+-ATPase Concentration and Fiber Type Distribution After Spinal Cord Injury. Muscle Nerve. 2004;29(1):38-45. PubMed PMID: 14694496.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Na+,K+-ATPase concentration and fiber type distribution after spinal cord injury. AU - Ditor,D S, AU - Hamilton,S, AU - Tarnopolsky,M A, AU - Green,H J, AU - Craven,B C, AU - Parise,G, AU - Hicks,A L, PY - 2003/12/25/pubmed PY - 2004/2/10/medline PY - 2003/12/25/entrez SP - 38 EP - 45 JF - Muscle & nerve JO - Muscle Nerve VL - 29 IS - 1 N2 - Complete spinal cord injury (SCI) is characterized, in part, by reduced fatigue-resistance of the paralyzed skeletal muscle during stimulated contractions, but the underlying mechanisms are not fully understood. The effects of complete SCI on skeletal muscle Na(+),K(+)-adenosine triphosphatase (ATPase) concentration, and fiber type distribution were therefore investigated. Six individuals (aged 32.0 +/- 5.3 years) with complete paraplegia (T4-T10; 1-19 years since injury) participated. There was a significantly lower Na(+),K(+)-ATPase concentration in the paralyzed vastus lateralis (VL) when compared to either the subjects' own unaffected deltoid or literature values (from our laboratory, utilizing the same methodology) of VL Na(+),K(+)-ATPase concentration for the healthy able-bodied (141.6 +/- 50.0, 213.4 +/- 23.9, 339 +/- 16 pmol/g wet wt., respectively; P < 0.05). There was also a significant negative correlation between the Na(+),K(+)-ATPase concentration in the paralyzed VL and years since injury (r = -0.75, P < 0.05). These findings are clinically relevant as they suggest that reductions in Na(+),K(+)-ATPase contribute to the fatigability of paralyzed muscle after SCI. Unexpectedly, the VL muscles of our subjects had a higher proportion of their area represented by type I fibers compared to literature values for the VL of the healthy able-bodied (52.6 +/- 25.3% vs. 36 +/- 11.3%, respectively; P < 0.05). As all our subjects had upper motor neuron injuries and, therefore, experienced muscle spasticity, our findings warrant further investigation into the relationship between muscle spasticity and fiber type expression after SCI. SN - 0148-639X UR - https://www.unboundmedicine.com/medline/citation/14694496/Na+K+_ATPase_concentration_and_fiber_type_distribution_after_spinal_cord_injury_ DB - PRIME DP - Unbound Medicine ER -