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Excess recovery heat production by isolated muscles from mice overexpressing uncoupling protein‐3
Author(s) -
Curtin N. A.,
Clapham J. C.,
Barclay C. J.
Publication year - 2002
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.2002.021964
Subject(s) - isometric exercise , chemistry , atpase , creatine kinase , biochemistry , biophysics , biology , enzyme , physiology
Contractile and energetic performance of bundles of muscle fibres from the soleus of mice overexpressing uncoupling protein 3 (UCP‐3tg) were compared with the performance of bundles from wild‐type mice. Force and heat production were measured during a series of thirty 0.2 s isometric tetani at L o , the length optimal for force. UCP‐3tg fibres were as strong as the wild‐type and maintained force in the series equally well; in the first tetanus force was 116.9 ± 15.1 and 133.3 ± 19.7 mN mm −2 respectively (all values means ± s.e.m. , n = 6 for UCP‐3tg and n = 5 for wild‐type). Heat production was partitioned into initial heat (due to contractile ATPases and the creatine kinase reaction) and recovery heat (due to other ATP‐supplying processes) and expressed relative to the first cycle total heat. Initial heat production was similar for the UCP‐3tg and wild‐type fibres, decreasing during the series from 0.799 ± 0.052 to 0.661 ± 0.061 relative units (UCP‐3tg), and from 0.806 ± 0.024 to 0.729 ± 0.039 relative units (wild‐type). In both types the recovery heat was small at the start of the series and increased as the series progressed. At the end of the series, recovery heat production by UCP‐3tg fibres, 1.575 ± 0.246 relative units, was twice that of the wild‐type fibres, 0.729 ± 0.072 relative units. The extra recovery heat represents inefficient recovery in UCP‐3tg fibres. This is the first direct evidence of enhanced energy dissipation as heat when UCP‐3tg is overexpressed.