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Oxygen consumption kinetics are related to mitochondrial content but not fiber type in single Xenopus skeletal muscle fibers
Author(s) -
Wust Rob CI,
Jaspers Richard T,
Laarse Willem J,
Rossiter Harry B
Publication year - 2011
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.25.1_supplement.1058.1
Subject(s) - xenopus , skeletal muscle , chemistry , fiber , oxygen , oxidative phosphorylation , isometric exercise , mitochondrion , biophysics , kinetics , fiber type , skeletal muscle fibers , medicine , biochemistry , anatomy , biology , physics , organic chemistry , quantum mechanics , gene
It is generally accepted that oxygen consumption (VO 2 ) kinetics are rapid in slow‐twitch skeletal muscle fibers (compared to fast‐twitch), suggesting a tight coupling between energy demand and oxidative energy provision. Whether this is related to VO 2 dynamic control features that differ between fiber types, or more simply, to a greater mitochondrial density in slow‐twitch fibers, is currently unclear. To address this we determined the relationship between succinate dehydrogenase (SDH) activity (for mitochondrial content) and the VO 2 time constant (τVO 2 ) in muscle fibers with different ATPase activity. VO 2 was measured in intact single Xenopus laevis fibers (n = 6) using a 170 μl chamber and a fast‐response PO 2 electrode (response τ = 2 s; Elzinga & van der Laarse J Physiol 399: 405–418, 1988) at 20 °C. VO 2 was measured every 1 s on transition from rest to isometric contractions at VO 2 max, and τVO 2 was estimated with a confidence of <2 s. SDH activity and fiber type were determined histochemically. τVO 2 averaged (± SD) 58 ± 12 s and was negatively correlated to SDH activity (4.50 ± 1.31 ·10 −6 ΔA 660 .μm −1 .s −1 ; r = −0.58) and VO 2 max (0.095 ± 0.049 nmol.mm −3 .s −1 ; r = −0.75), but was independent of fiber type (τVO 2 in type 3 = 58 s; mixed = 59 s; type 2 = 56 s). These data suggest that mitochondrial density is a key determinant of τVO 2 and that the control of VO 2 kinetics does not vary between fiber types per se . Support BBSRC (BB/F019521/1)