The effect of intracellular ph on force development depends on
temperature in intact skeletal muscle from mouse.
Wiseman, Robert W., Thomas W. Beck, and P. Bryant Chase.
Departments of Radiology and Physiology and Biophysics, University
of Washington Medical Center, Seattle, WA 98195 and Primate Field
Station, University of Washington, Medical Lake, WA 99011
APStracts 3:0065C, 1996.
The cellular mechanism of muscle fatigue is still in debate. Opposite
conclusions regarding the role of intracellular pH (pHi) in fatigue
have been drawn from skinned fiber versus isolated perfused muscle
studies. Since these experiments are typically performed at different
temperatures, we tested the hypothesis that temperature alters the
effects of pH on force. Tetanic force of isolated mouse extensor
digitorum longus (EDL) was measured at temperatures between 13oC and
25oC in either normo- (5% CO2) or hyper-capnea (25% CO2). Hypercapnea
decreased pHi (monitored by 31P-NMR spectroscopy) by the same amount
at both 15 and 25oC. However, inhibition of force by hypercapnea was
greater at the lower temperature. A similar pattern of temperature
dependent inhibition of force by pH was observed in glycerinated
fibers from rabbit psoas at maximum Ca2+ activation. We conclude that
temperature differences are responsible for disparate conclusions on
the role of pHi in muscle fatigue. Based on our results we suggest
that changes in pHi may have little or no role in the loss in force
production associated with muscular fatigue at physiologic
temperatures.
Received 2 October 1995; accepted in final form 16 February 1996.
APS Manuscript Number C598-5.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 13 March 96