Faculty Collaboration Database

The depressive effect of Pi on the force-pCa relationship in skinned single muscle fibers is temperature dependent. Am J Physiol Cell Physiol 2006 Apr;290(4):C1041-50

Date

11/12/2005

Pubmed ID

16282195

DOI

10.1152/ajpcell.00342.2005

Scopus ID

2-s2.0-33646385633 (requires institutional sign-in at Scopus site)   78 Citations

Abstract

Increases in P(i) combined with decreases in myoplasmic Ca(2+) are believed to cause a significant portion of the decrease in muscular force during fatigue. To investigate this further, we determined the effect of 30 mM P(i) on the force-Ca(2+) relationship of chemically skinned single muscle fibers at near-physiological temperature (30 degrees C). Fibers isolated from rat soleus (slow) and gastrocnemius (fast) muscle were subjected to a series of solutions with an increasing free Ca(2+) concentration in the presence and absence of 30 mM P(i) at both low (15 degrees C) and high (30 degrees C) temperature. In slow fibers, 30 mM P(i) significantly increased the Ca(2+) required to elicit measurable force, referred to as the activation threshold at both low and high temperatures; however, the effect was twofold greater at the higher temperature. In fast fibers, the activation threshold was unaffected by elevating P(i) at 15 degrees C but was significantly increased at 30 degrees C. At both low and high temperatures, 30 mM P(i) increased the Ca(2+) required to elicit half-maximal force (pCa(50)) in both slow and fast fibers, with the effect of P(i) twofold greater at the higher temperature. These data suggest that during fatigue, reductions in the myoplasmic Ca(2+) and increases in P(i) act synergistically to reduce muscular force. Consequently, the combined changes in these ions likely account for a greater portion of fatigue than previously predicted based on studies at lower temperatures or high temperatures at saturating Ca(2+) levels.

Author List

Debold EP, Romatowski J, 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
Calcium
Male
Muscle Contraction
Muscle Fibers, Fast-Twitch
Muscle Fibers, Slow-Twitch
Phosphates
Rats
Rats, Sprague-Dawley
Stress, Mechanical
Temperature