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Prolonged force increase following a high-frequency burst is not due to a sustained elevation of [[[Ca.sup.2+]].sub.i]

Authors :
Abbate, F.
Bruton, J.D.
De Haan, A.
Westerblad, H.
Source :
The American Journal of Physiology. July, 2002, Vol. 283 Issue 1, pC42, 6 p.
Publication Year :
2002

Abstract

Prolonged force increase following a high-frequency burst is not due to a sustained elevation of [[[Ca.sup.2+].sub.i]. Am J Physiol Cell Physiol 283: C42-C47, 2002; 10.1152/ajpcell. 00416.2001.--A brief high-frequency burst of action potentials results in a sustained force increase in skeletal muscle. The present study investigates whether this force potentiation is the result of a sustained increase of the free myoplasmic [[Ca.sup.2+]] ([[[Ca.sup.2+]].sub.i]). Single fibers from mouse flexor brevis muscles were stimulated with three impulses at 150 Hz (triplet) at the start of a 350-ms tetanus or in the middle of a 700-ms tetanus; the stimulation frequency of the rest of the tetanus ranged from 20 to 60 Hz. After the triplet, force was significantly (P < 0.05) increased between 17 and 20% when the triplet was given at the start of the tetanus and between 5 and 18% when the triplet was given in the middle (n = 7). However, during this potentiation, [[[Ca.sup.2+]].sub.i] was not consistently increased. Hence, the increased force following a high-frequency burst is likely due to changes in the myofibrillar properties. force potentiation; excitation contraction coupling; mechanical output; skeletal muscle; [Ca.sup.2+]

Details

ISSN :
00029513
Volume :
283
Issue :
1
Database :
Gale General OneFile
Journal :
The American Journal of Physiology
Publication Type :
Academic Journal
Accession number :
edsgcl.90098386