Rat diaphragm mitochondria have lower intrinsic respiratory rates than mitochondria in limb muscles

Mary L. Garcia-Cazarin, Jorge L. Gamboa, Francisco H. Andrade

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


The mitochondrial content of skeletal muscles is proportional to activity level, with the assumption that intrinsic mitochondrial function is the same in all muscles. This may not hold true for all muscles. For example, the diaphragm is a constantly active muscle; it is possible that its mitochondria are intrinsically different compared with other muscles. This study tested the hypothesis that mitochondrial respiration rates are greater in the diaphragm compared with triceps surae (TS, a limb muscle). We isolated mitochondria from diaphragm and TS of adult male Sprague Dawley rats. Mitochondrial respiration was measured by polarogra-phy. The contents of respiratory complexes, uncoupling proteins 1, 2, and 3 (UCP1, UCP2, and UCP3), and voltage-dependent anion channel 1 (VDAC1) were determined by immunoblotting. Complex IV activity was measured by spectrophotometry. Mitochondrial respiration states 3 (substrate and ADP driven) and 5 (uncoupled) were 27 ± 8% and 24 ± 10%, respectively, lower in diaphragm than in TS (P < 0.05 for both comparisons). However, the contents of respiratory complexes III, IV, and V, UCP1, and VDAC1 were higher in diaphragm mitochondria (23 ± 6, 30 ± 8, 25 ± 8, 36 ± 15, and 18 ± 8% respectively, P < 0.04 for all comparisons). Complex IV activity was 64 ± 16% higher in diaphragm mitochondria (P < 0.01). Mitochondrial UCP2 and UCP3 content and complex I activity were not different between TS and diaphragm. These data indicate that diaphragm mitochondria respire at lower rates, despite a higher content of respiratory complexes. The results invalidate our initial hypothesis and indicate that mitochondrial content is not the only determinant of aerobic capacity in the diaphragm. We propose that UCP1 and VDAC1 play a role in regulating diaphragm aerobic capacity.

Original languageEnglish
Pages (from-to)1311-1315
Number of pages5
JournalAmerican Journal of Physiology - Regulatory Integrative and Comparative Physiology
Issue number6
StatePublished - Jun 2011


  • Mitochondria respiration
  • Respiratory muscles
  • Triceps surae
  • Uncoupling proteins

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)


Dive into the research topics of 'Rat diaphragm mitochondria have lower intrinsic respiratory rates than mitochondria in limb muscles'. Together they form a unique fingerprint.

Cite this