Faculty Collaboration Database

Effects of fatiguing stimulation on intracellular Na+ and K+ in frog skeletal muscle. J Appl Physiol (1985) 1996 Aug;81(2):679-85

Date

08/01/1996

Pubmed ID

8872634

DOI

10.1152/jappl.1996.81.2.679

Scopus ID

2-s2.0-0029785783 (requires institutional sign-in at Scopus site)   56 Citations

Abstract

The purpose of this study was to describe the alterations in the intracellular concentrations of sodium ([Na+]i) and potassium ([K+]i) and the membrane potential (Em) as a result of fatiguing stimulation of the frog semitendinosus muscle and to relate these changes to the alterations in the sarcolemma action potential and force-generating ability of the muscle. [Na+]i and [K+]i were measured by using ion-selective microelectrodes. Before stimulation (100-ms trains at 150 Hz, 1 stimulus/s for 5 min), [Na+]i, [K+]i, and Em were 16 +/- 1 mM, 142 +/- 5 mM, and -83 +/- 1 mV, respectively. As a result of stimulation, [Na+]i rose to 49 +/- 6 mM and recovered to 16 +/- 2 mM with a time constant (tau) of 70 s.[K+]i fell to 97 +/- 8 mM as a result of stimulation, then recovered to 148 +/- 5 mM with tau = 56 s. Em depolarized to -74 +/- 3 mV then recovered to -83 +/- 2 mV with tau = 53 s. The Na+/K+ permeability ratio of the resting membrane fell 3%, whereas at the peak of the action potential the permeability ratio fell 38%. A previous study using the same muscle and stimulation protocol showed force to recover with a fast initial phase (approximately 2 min) and a much slower second phase (approximately 50 min). The recovery of [Na+]i, [K+]i, and Em was similar to the fast phase of force recovery; thus the altered Na+ and K+ concentration gradient across the sarcolemma and t-tubular membrane may contribute to this component of fatigue. The possible fatigue mechanisms induced by the altered ionic gradients include 1) complete block of the action potential propagation; 2) depolarization-induced inactivation of t-tubular charge movement; and 3) a reduced magnitude of the t-tubular charge due to the lower action potential spike potential.

Author List

Balog EM, 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

Action Potentials
Animals
Calibration
Electric Stimulation
In Vitro Techniques
Membrane Potentials
Microelectrodes
Muscle Contraction
Muscle, Skeletal
Potassium
Rana pipiens
Sarcolemma
Sodium