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) All Versions of this Article: 294/4/C1113    most recent ajpcell.00063.2008v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Colombini, B. Articles by Bagni, M. A. PubMed PubMed Citation Articles by Colombini, B. Articles by Bagni, M. A.

MEMBRANE TRANSPORTERS, ION CHANNELS, AND PUMPS

Effect of temperature on cross-bridge properties in intact frog muscle fibers

Dipartimento di Scienze Fisiologiche and Istituto Interuniversitario di Miologia, Università degli Studi di Firenze, Firenze, Italy

Submitted 6 February 2008 ; accepted in final form 20 February 2008

It is well known that the force developed by skeletal muscles increases with temperature. Despite the work done on this subject, the mechanism of force potentiation is still debated. Most of the published papers suggest that force enhancement is due to the increase of the individual cross-bridge force. However, reports on skinned fibers and single-molecule experiments suggest that cross-bridge force is temperature independent. The effects of temperature on cross-bridge properties in intact frog fibers were investigated in this study by applying fast stretches at various tension levels (P) on the tetanus rise at 5°C and 14°C to induce cross-bridge detachment. Cross-bridge number was measured from the force (critical force, P_c) needed to detach the cross-bridge ensemble, and the average cross-bridge strain was calculated from the sarcomere elongation needed to reach P_c (critical length, L_c). Our results show that P_c increased linearly with the force developed at both temperatures, but the P_c/P ratio was considerably smaller at 14°C. This means that the average force per cross bridge is greater at high temperature. This mechanism accounts for all the tetanic force enhancement. The critical length L_c was independent of the tension developed at both temperatures but was significantly lower at high temperature suggesting that cross bridges at 14°C are more strained. The increased cross-bridge strain accounts for the greater average force developed.

force enhancement; fast stretches