J Physiol Wellcome Trust-funded researchers
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
QUICK SEARCH:   [advanced]


     

J Physiol Vol 496, Issue Pt 2 pp 503-519
Copyright © 1996 by The Physiological Society
This Article
Right arrow Full Text (PDF)
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Buschman, H P
Right arrow Articles by Elzinga, G
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Buschman, H P
Right arrow Articles by Elzinga, G

Force-dependent and force-independent heat production in single slow- and fast-twitch muscle fibres from Xenopus laevis.

 H P Buschman, W J van der Laarse, G J Stienen and G Elzinga

Laboratory for Physiology, Vrije Universiteit, Amsterdam, The Netherlands. buschman@mit.edu

1. The origin of labile heat production, i.e. a heat component which rapidly decays after the onset of stimulation, and of stable (maintenance) heat production was investigated in intact single fast-twitch (type 1) and slow-twitch (type 3) iliofibularis muscle fibres from Xenopus laevis, at 20 degrees C, by varying stimulation frequency and by varying sarcomere length and the concentration of 2,3-butanedione 2-monoxime (BDM) added. 2. The labile heat produced consisted of a force-independent and a force-dependent part. The average parvalbumin (PA) content found in type 1 fibre bundles (0.84 +/- 0.08 mM; mean +/- S.E.M.; n = 5) and in type 3 fibre bundles (0.12 +/- 0.02 mM; n = 5) indicates that the force-independent labile heat is explained by Ca(2+)-Mg2+ exchange on PA, and amounts to a molar enthalpy change of -78 kJ (molPA)-1. 3. Force-dependent labile heat during fused contractions was similar to the calculated heat production resulting from the formation of force-generating cross-bridges, assuming an enthalpy change associated with cross-bridge formation of -30 kJ mol-1. 4. Activation heat, i.e. the part of the total stable heat that is not related to the contractile apparatus, and of which the calcium sequestration by the sarcoplasmic reticulum is the most important contributor, determined by varying sarcomere length or BDM concentration, was identical. For fused contractions the fraction activation heat of the stable maintenance rate of heat production was 34 +/- 4% (mean +/- S.E.M.; n = 13) in type 1 fibres, and 52 +/- 4% (n = 15) in type 3 fibres. In unfused contractions this was 48 +/- 5% (n = 13) in type 1 fibres, and 35 +/- 2% (n = 11) in type 3 fibres. 5. From the force-dependent stable rate of heat production the economy of cross-bridge cycling, expressed as the force-time integral for a single myosin head per ATP molecule hydrolysed, was calculated. It followed that cross-bridge interaction in type 3 fibres is more economical than in type 1 fibres, and that fused contractions are more economical than unfused contractions.




This article has been cited by other articles:


Home page
 Am. J. Physiol. Regul. Integr. Comp. Physiol.Home page
B. Walsh, R. A. Howlett, C. M. Stary, C. A. Kindig, and M. C. Hogan
Measurement of activation energy and oxidative phosphorylation onset kinetics in isolated muscle fibers in the absence of cross-bridge cycling
Am J Physiol Regulatory Integrative Comp Physiol, June 1, 2006; 290(6): R1707 - R1713.
[Abstract] [Full Text] [PDF]


HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
Copyright © 1996 The Physiological Society.