Faculty Collaboration Database

Low cell pH depresses peak power in rat skeletal muscle fibres at both 30 degrees C and 15 degrees C: implications for muscle fatigue. J Physiol 2006 Sep 15;575(Pt 3):887-99

Date

07/01/2006

Pubmed ID

16809373

Pubmed Central ID

PMC1995695

DOI

10.1113/jphysiol.2006.106732

Scopus ID

2-s2.0-33748314631 (requires institutional sign-in at Scopus site)   93 Citations

Abstract

Historically, an increase in intracellular H(+) (decrease in cell pH) was thought to contribute to muscle fatigue by direct inhibition of the cross-bridge leading to a reduction in velocity and force. More recently, due to the observation that the effects were less at temperatures closer to those observed in vivo, the importance of H(+) as a fatigue agent has been questioned. The purpose of this work was to re-evaluate the role of H(+) in muscle fatigue by studying the effect of low pH (6.2) on force, velocity and peak power in rat fast- and slow-twitch muscle fibres at 15 degrees C and 30 degrees C. Skinned fast type IIa and slow type I fibres were prepared from the gastrocnemius and soleus, respectively, mounted between a force transducer and position motor, and studied at 15 degrees C and 30 degrees C and pH 7.0 and 6.2, and fibre force (P(0)), unloaded shortening velocity (V(0)), force-velocity, and force-power relationships determined. Consistent with previous observations, low pH depressed the P(0) of both fast and slow fibres, less at 30 degrees C (4-12%) than at 15 degrees C (30%). However, the low pH-induced depressions in slow type I fibre V(0) and peak power were both significantly greater at 30 degrees C (25% versus 9% for V(0) and 34% versus 17% for peak power). For the fast type IIa fibre type, the inhibitory effect of low pH on V(0) was unaltered by temperature, while for peak power the inhibition was reduced at 30 degrees C (37% versus 18%). The curvature of the force-velocity relationship was temperature sensitive, and showed a higher a/P(0) ratio (less curvature) at 30 degrees C. Importantly, at 30 degrees C low pH significantly depressed the ratio of the slow type I fibre, leading to less force and velocity at peak power. These data demonstrate that the direct effect of low pH on peak power in both slow- and fast-twitch fibres at near-in vivo temperatures (30 degrees C) is greater than would be predicted based on changes in P(0), and that the fatigue-inducing effects of low pH on cross-bridge function are still substantial and important at temperatures approaching those observed in vivo.

Author List

Knuth ST, Dave H, Peters JR, Fitts RH

Author

Robert Fitts PhD Professor in the Biological Sciences department at Marquette University

MESH terms used to index this publication - Major topics in bold

Animals
Hydrogen-Ion Concentration
In Vitro Techniques
Male
Muscle Contraction
Muscle Fatigue
Muscle Fibers, Fast-Twitch
Muscle Fibers, Slow-Twitch
Muscle, Skeletal
Rats
Rats, Sprague-Dawley
Temperature