HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Rome, L. C. Articles by Klimov, A. A. Search for Related Content PubMed PubMed Citation Articles by Rome, L. C. Articles by Klimov, A. A.

Superfast contractions without superfast energetics: ATP usage by SR-Ca²⁺ pumps and crossbridges in toadfish swimbladder muscle

Lawrence C. Rome and Andrei A. Klimov

1. The rate at which an isometrically contracting muscle uses energy is thought to be proportional to its twitch speed. In both slow and fast muscles, however, a constant proportion (25-40 %) of the total energy has been found to be used by SR-Ca²⁺ pumps and the remainder by crossbridges. We examined whether SR-Ca²⁺ pumps account for a larger proportion of the energy in the fastest vertebrate muscle known (the toadfish swimbladder), and whether the swimbladder muscle utilizes energy at the superfast rate one would predict from its mechanics.

2. The ATP utilization rates of the SR-Ca²⁺ pumps and crossbridges were measured using a coupled assay system on fibres skinned with saponin. Surprisingly, despite its superfast twitch speed, the ATP utilization rate of swimbladder was no higher than that of much slower fast-twitch amphibian muscles.

3. The swimbladder achieves tremendous twitch speeds with a modest steady-state ATP utilization rate by employing two mechanisms: having a small number of attached crossbridges and probably utilizing intracellular Ca²⁺ buffers (parvalbumin) to spread out the time over which Ca²⁺ pumping can occur.

4. Finally, although the total ATP utilization rate was not as rapid as expected, the relative proportions used by SR-Ca²⁺ pumps and the crossbridges were similar to other muscles.

This article has been cited by other articles:

				W. M. Kier and F. H. Schachat Muscle specialization in the squid motor system J. Exp. Biol., January 15, 2008; 211(2): 164 - 169. [Abstract] [Full Text] [PDF]

				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]

				A. F. Mensinger and M. E. Tubbs Effects of Temperature and Diet on the Growth Rate of Year 0 Oyster Toadfish, Opsanus tau. Biol. Bull., February 1, 2006; 210(1): 64 - 71. [Abstract] [Full Text] [PDF]

				T. Kobayashi, T. Daimon, I. Shirakawa, S. Chaen, and H. Sugi Electrical and mechanical properties and mode of innervation in scorpionfish sound-producing muscle fibres J. Exp. Biol., October 1, 2004; 207(21): 3757 - 3763. [Abstract] [Full Text] [PDF]

				I. S. Young, C. L. Harwood, and L. C. Rome Cross-bridge blocker BTS permits direct measurement of SR Ca2+ pump ATP utilization in toadfish swimbladder muscle fibers Am J Physiol Cell Physiol, October 1, 2003; 285(4): C781 - C787. [Abstract] [Full Text] [PDF]

				K. E. Conley and S. L. Lindstedt Energy-saving mechanisms in muscle: the minimization strategy J. Exp. Biol., August 1, 2002; 205(15): 2175 - 2181. [Abstract] [Full Text] [PDF]