The Depressive Effect of P_i on the Force-pCa Relationship in Skinned Single Muscle Fibers Is Temperature Dependent

Authors

Edward Patrick Debold, Marquette University
Janell Romatowski, Marquette University
Robert Fitts, Marquette UniversityFollow

Document Type

Article

Language

eng

Format of Original

10 p.

Publication Date

11-9-2005

Publisher

American Physiological Society

Source Publication

American Journal of Physiology - Cell Physiology

Source ISSN

0002-9513

Abstract

Increases in P_i combined with decreases in myoplasmic Ca2+ 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_ion the force-Ca²⁺ relationship of chemically skinned single muscle fibers at near-physiological temperature (30°C). Fibers isolated from rat soleus (slow) and gastrocnemius (fast) muscle were subjected to a series of solutions with an increasing free Ca²⁺ concentration in the presence and absence of 30 mM P_iat both low (15°C) and high (30°C) temperature. In slow fibers, 30 mM P_i significantly increased the Ca²⁺ 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°C but was significantly increased at 30°C. At both low and high temperatures, 30 mM P_i increased the Ca²⁺ required to elicit half-maximal force (pCa₅₀) 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 Ca²⁺ 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 Ca²⁺ levels.

Comments

Accepted version. American Journal of Physiology - Cell Physiology, Volume 29, (November 2005): C1041-C1050. DOI. © 2005 American Physiological Society. Used with permission.

Recommended Citation

Debold, Edward Patrick; Romatowski, Janell; and Fitts, Robert, "The Depressive Effect of P_i on the Force-pCa Relationship in Skinned Single Muscle Fibers Is Temperature Dependent" (2005). Biological Sciences Faculty Research and Publications. 37.
https://epublications.marquette.edu/bio_fac/37